United States Geography - language, government, economy, cities, history, tourism, people, education, religion

Read about United States Geography: language, government, economy, cities, history, tourism, people, education, religion, agriculture, climate ...


United States Geography, study of the land, physical features, and climate of the United States of America, and the interaction between these natural features and the plants, animals, and people that live in the country.

The United States of America is a federal republic on the continent of North America. It has an area of 9,826,630 sq km (3,794,083 sq mi) and is the third largest country in the world after Russia and Canada. The estimated U.S. population for the year 2009 is 307,212,120, third in the world behind China and India.

The United States consists of 48 contiguous states and the noncontiguous states of Alaska and Hawaii. In addition, the United States includes a number of outlying areas, such as the Commonwealth of Puerto Rico and the Virgin Islands of the United States, which are located on the Caribbean Sea, and the islands of American Samoa and Guam, located in the Pacific Ocean. The national capital is Washington, D.C., located along the banks of the Potomac River between the states of Maryland and Virginia.

The 50 U.S. states vary widely in size and population. The largest states in area are Alaska at 1,717,854 sq km (663,267 sq mi), followed by Texas, and California. The smallest state is Rhode Island, with an area of 4,002 sq km (1,545 sq mi). The state with the largest population is California (36,756,666, 2008 estimate), followed by Texas, and New York. Only 532,668 people (2008 estimate) live on the plateaus and rugged mountains of Wyoming, the least populous state.

Each state is subdivided into counties, with the exception of Louisiana, where comparable political units are called parishes. Within these counties and parishes, there are communities that range in size from small villages to towns to cities. Extensive areas of urban sprawl exist in larger metropolitan areas such as Los Angeles, California; Chicago, Illinois; and New York City.

This is one of seven major articles that together provide a comprehensive discussion of the United States of America. For more information on the United States, please see the other six major articles: United States (Overview), United States (People), United States (Culture), United States (Economy), United States (Government), and United States (History).


Cultural Diversity

The United States is certainly one of the most diverse countries of the world, both from a cultural and an environmental perspective. The land that is now the United States was home to diverse cultures when the first Europeans and Africans arrived. It was inhabited by a variety of Native American peoples who spoke more than 300 different languages. The Europeans and Africans added their own varying cultures to this diversity.

The 13 colonies they founded along the eastern seaboard became the United States in the late 18th century. see United States (History). During the following century, the new nation added huge chunks of territory, and millions of immigrants arrived, mainly from Europe and especially during the years from 1860 to 1914. A second migration occurred in the Southwest, where Hispanics pushed northward from Mexico, leaving an indelible imprint. see Immigration. In addition, slaves were brought from Africa to work on agricultural estates in the South, where they formed a large percentage of the population. see Slavery in the United States.

Of those who chose to come to the United States, many saw it as a land of plenty, and certainly that was true. However, many Americans faced extraordinary hardships as they adapted to a natural and cultural environment that was sometimes harsh and demanding.

Geographic Diversity

During the settlement of the nation, immigrants moved westward across the United States and found a rich and varied natural environment. From the original coastal colonies, settlers made their way over the Appalachian Mountains beginning in the 1700s. Beyond the mountains lay the vast rolling territory drained by the Mississippi River and the Great Lakes. There settlers encountered the rich farmlands of the Ohio Valley, the Mississippi Delta, and the Great Plains. For decades, the rugged peaks of the Rocky Mountains and the arid landscape of the Southwest discouraged movement further west. In the mid-1800s, however, spurred by the discovery of gold in California, determined settlers followed trails through the mountain passes to reach the West Coast. In the valleys of California and Oregon, they found productive agricultural land, and they began harvesting the timber reserves from the untouched forests of the Pacific Northwest. The purchase of Alaska in 1867 added a mountainous northern territory rich in natural resources. The annexation of Hawaii in 1898 gave the United States what would be its only tropical state. The United States has been blessed with many natural advantages, such as climates favorable for agriculture, extensive internal waterways, and abundant natural resources.

All four of the world’s most productive agricultural climates are found in the United States. These climatic regions display a favorable mix of rain and sun as well as a long growing season, and together, they cover more than a third of the country. Favorable climates have allowed farmers to produce vast quantities of grain for human consumption and crops to feed animals. These remarkable climatic areas make the United States one of the world’s leading agricultural countries.

Another major natural advantage—one that is taken for granted by most Americans—is that the major river systems (the Mississippi, Missouri, Ohio, Colorado, and Río Grande systems) flow south. If these rivers flowed north, as rivers do in Russian Siberia, ice and frozen soil would block the meltwater, causing floods that would saturate the land and render it unusable for agriculture. Instead, when spring thaws arrive in the interior mountains of the United States, meltwater flows unimpeded through the river systems to the warm waters of the Gulf of Mexico or the Gulf of California. This almost uninterrupted flow of water provides ample supplies for drinking water and for crop irrigation and industrial production.

The United States has many other natural advantages. A wide array of valuable mineral resources, such as oil, natural gas, iron ore, coal, lead, zinc, phosphate, silver, and copper, benefits mining and industry. The shallow waters along the coastline, known as the continental shelf, serve as a rich breeding ground for marine life, which promotes commercial and sport fishing. The comprehensive network of rivers also provides transportation routes for bulk cargo and the potential for the development of hydroelectricity.

Americans and the Environment

The people of the United States used this remarkable array of natural resources to build their society. At first, and for many years, the United States was primarily an agricultural society. Until the second decade of the 20th century, most Americans lived and worked on farms. Rich agricultural land allowed Americans to produce, process, and deliver enough food, not only for the United States, but also for millions of people in other countries.

Americans developed the land’s natural resources in many other ways as well. They used water from the nation’s vast river systems to irrigate arid land and to transport people and goods. They built harbors for ports along the coastlines in order to ship and receive goods from all over the world. They exploited the forests and the fisheries, building major industries providing goods for domestic consumption and for export.

Industry developed early in the United States. During the first half of the 19th century, the Industrial Revolution spread from Europe and stimulated the rapid growth of industry in the Northeast. Raw materials were brought to the Northeast from other parts of the country by ship and by a rapidly expanding rail system. Industrial plants processed the raw material into finished products for export and for domestic consumption.

From 1850 to 1920, industrial expansion continued and moved westward. Chicago, Illinois, became the leading meatpacking center of the United States. Pittsburgh, Pennsylvania, became synonymous with steel. Detroit, Michigan, emerged as the automobile capital of the world. Other large U.S. cities developed their own specialties. By the beginning of World War I (1914-1918), America had become the world’s greatest industrial giant. see United States (History).

However, as Americans developed the land and its resources, they sometimes created environmental problems. Forests and natural grasslands began disappearing as early as colonial times (17th and 18th centuries), as settlers converted more and more wilderness into farmland. In the 20th century, urban sprawl and industrial expansion led to pollution of the air and water. A growing population, and its demands for a convenient lifestyle, generated tremendous amounts of pollution and waste. By the mid-1990s, Americans created 2.0 kg (4.3 lbs) of trash per person per day. Often the highest hill around a typical U.S. city consisted of the waste buried at the local sanitary landfill. See also Air Pollution; Water Pollution.

In the last 30 years of the 20th century, however, Americans have become more aware of environmental problems and have begun programs to reduce pollution and conserve natural areas. People also learned to recycle, to reuse resources, and to protect endangered species. See also Conservation.

From Diversity, a Unified Country

The United States resembles a colorful quilt stitched together from geographic regions that maintain unique cultural patterns. Life in rural Alabama, for example, is quite different from life in suburban California or in the highly urbanized environment of New York City. Despite these differences, however, the various regions of the United States mesh together to form a single fabric. An extensive transportation system, a sophisticated communications network, and a common culture bind the nation into an indivisible unit. The study of geography helps people understand the complicated mosaic of life in the United States and how despite their differences, Americans still exhibit characteristics of unity that make the United States a country very distinct from all the other nations in the world.


The Nature of Regions

When examining a large geographic unit, such as the United States, geographers often divide the country into smaller regions. Dividing into parts allows us to better understand unique areas of the nation and how they combine into a whole. By analyzing regions, geographers can better understand how humans occupy and use the surface of the earth.

Regions can vary greatly in size. A region may be as small as a backyard or as large as a continent. For instance, a salesman making business calls in an unfamiliar town will need to learn about a relatively small geographic region. On the other hand, a traveler making a trip around the world or a geographer compiling statistics about a large nation will examine a region of considerably larger scope. What is important is understand how knowledge of these regions helps us more fully appreciate the world in which we live.

Regions are not as clearly defined in our real lives as they are on our maps. Sharp and distinct borders are rare. Most boundaries are transitional as regions merge comfortably into each other. The characteristics that distinguish one region gradually give way to the characteristics of its neighbor. Nonetheless, each geographic region has specific characteristics that can be experienced in the real world and that clearly differentiate it from neighboring regions. Geographers have defined two kinds of regions—uniform and functional.

A uniform region is distinguished by some characteristic—such as climate, soil, landforms, language, religion, and social customs—that is common throughout the region. Some uniform regions are natural regions—their common characteristic is a feature of the natural environment. Examples include the Rocky Mountains or the Appalachians, which both have the common characteristic of mountains. The Pacific Northwest shares a common climate: It has wet weather and mild temperatures.

Other uniform regions are classified on the basis of human or cultural characteristics. Areas that are not physically different from neighboring geographic locations might be classified as distinct regions because of factors such as the type of economy, political organization, or historical background, or because the population shares a similar ethnic or national background, language, religion, or racial origin. Examples of such uniform regions include the Midwest, which has a common agricultural economy emphasizing the production of corn, hogs, and soybeans; the Amish religious communities of eastern Pennsylvania; the Chinatowns of New York and San Francisco; the concentrations of African Americans in most major cities; or the Hispanic cultural areas in Florida, Texas, New Mexico, Arizona, and California.

The second type of region is the functional region. A functional region is defined by its internal organization, which usually centers on some focal point. This could be a city, a school in an educational district, a shopping center in a large market area, or a large company that employs a sizeable number of workers.

The best example of a functional area is a Metropolitan Statistical Area (MSA). The United States Bureau of the Census identifies an MSA as a central city of 50,000 people or more, the surrounding county, and all adjacent counties in which jobs or commercial activity link a significant portion of the workforce to the central city or central county. There are presently almost 300 MSAs in the United States. They range from urban giants, such as the New York City MSA, which includes 18.3 million residents (1997 estimate) in the city and in the surrounding suburbs of New York, New Jersey, and Long Island, to smaller communities, such as Enid, Oklahoma, with a population of 57,000.

The concept of a functional region is important because the United States is an urban society, and people typically live or work in a central city. They shop in the city, read the urban newspaper, watch television programs that are broadcast from the central city, and generally identify themselves as residents of a particular metropolitan area.

Moreover, an area can be a cultural uniform region, a natural uniform region, and a functional region all at the same time. For example, the Heartland region of the United States, southeast of the Great Lakes, can be categorized as a uniform region due to common natural characteristics such as the prevalence of trees, the abundance of small bodies of water, and the presence of productive soils. It also shares common cultural factors such as a mixture of agricultural and manufacturing-based economies. The Heartland is a functional region as well, unified by a system of rails, roads, and inland waterways that serve the area’s economy.

Regional Breakdowns

The geographic regions described here are adapted from the work of professor Tom McKnight in his Regional Geography of the United States and Canada (1992). McKnight captures the dynamic nature of the natural and cultural environment in the United States and presents regions that make the task of understanding the geography of the United States a bit easier. These regions are largely uniform regions. Some display similar natural characteristics, for example climate and landforms. Others share cultural characteristics, such as economic or historical considerations. Taken together, these regions reflect the geographical tapestry of the United States. Separately, each region offers its own story, emphasizing how extraordinary differences can exist side by side and yet can meld into a single great country.


The region known as Megalopolis is a heavily populated area extending more than 800 km (500 mi) along a northeast-southwest axis from southern Maine to southern Virginia. Although it encompasses only 130,000 sq km (50,000 sq mi), or about 1 percent of the continent, Megalopolis held some 45 million people in the late 1990s, the second largest population of any U.S. region. It contains the world’s greatest concentration of urban areas.

Three characteristics define Megalopolis as a distinct region: high population density, major urban centers growing toward one another, and a large demand for primary goods that are brought in from other regions. Moreover, it is a region of social and economic superlatives—urban conveniences and problems, great wealth and poverty, high population concentrations, and one of the world’s most varied population mixes.

The region sits on the coastal plain along the northeast edge of the United States. The eastern boundary of Megalopolis is the Atlantic shoreline. On the western boundary of Megalopolis, high urban population densities and land-use patterns fade gradually into the lower population densities and land-use patterns of rural areas. The inland boundary is defined toward the south by the Appalachian hill lands and in the north by a transition zone that gradually gives way to the rural communities of upstate New York and northern New England.

The western portion of Megalopolis appears quite different from the skyscrapers and urban frenzy of the east. The small farms and gentle hills, however, serve the east with agricultural products and with quiet, beautiful scenery that provides a welcome escape for city dwellers whose day-to-day contact with the natural environment is practically nonexistent.

Natural Features

The most widespread aspect of the regional environment is the sea and its boundary with the land. Waterfront features include irregular coastlines; prominent peninsulas such as Cape Cod in Massachusetts, Cape May in New Jersey, and the Delmarva Peninsula of Chesapeake Bay; numerous offshore islands; and rivers that flow into the ocean in a variety of shapes and patterns.

Geologically, Megalopolis rests on a coastal plain, under which are unconsolidated sediments. Beneath these sediments is a base of ancient igneous and metamorphic rocks. Thousands of years ago, geological uplift produced a series of broad, open valleys. During the last Ice Age, glaciers scoured and flattened the northern parts of the coastal plain. The glaciers rounded the contours of the mountains and shaped a terrain of low rolling hills before they receded about 10,000 years ago. Long Island, New York, which extends east from New York City parallel to the coast of Connecticut, marks the southern limit of the last great ice sheet to move through the area. The land that makes up the island consists of earth and stone pushed southward by the ice and left behind when the glacier receded.

Most of the rivers in the region are fairly short and do not allow for inland navigation over long distances. However, important commercial transportation routes are found on some rivers. The Erie Canal joins the Hudson River in New York to create a passageway to the Great Lakes via Lake Erie, thus providing a valuable water transport route to the central regions of the United States. Canals also link the rivers of Delaware and Chesapeake bays.

Natural vegetation tends to be a mixture of trees and low brush, and soils are typically thin and infertile. However, agriculture abounds because of the urban demand for produce, the favorable climate, and the generous application of fertilizer.


Megalopolis lies along a busy oceanic route that extends across the North Atlantic to Western Europe. The presence of the sea has played an important role in the region’s economy since the colonial period. Early merchants transported goods via ocean trade routes, while rivers and land routes promoted trade with interior regions of the colonies and promoted economic growth. Trade and commerce were leading generators of wealth until the mid-1800s, when manufacturing became dominant. After World War II (1939-1945), the basis of the region’s economy shifted to service industries.

In the late 1990s, service industries remained the basis of the region’s economy. Megalopolis houses the headquarters of 33 percent of the largest industrial corporations in the nation, 28 percent of the largest retailing companies, 44 percent of the largest life insurance companies, and 60 percent of the largest diversified financial companies.

Tourism is also important throughout this region. New York City is one of the top tourist attractions in the nation for international travelers. Almost continuous beaches attract summer visitors, who support resort towns. Most states in the region have capitalized on their rich historical background to attract tourism.

Agriculture is important to meeting the demand for food from this large urban area. Commercial fishing has declined, though the region still accounts for about one-quarter of the U.S. catch. Chesapeake Bay yields more crabmeat than all other parts of the country combined.


The proximity to the ocean has also had a lasting effect on the population. Megalopolis was the first region of the country to be settled by immigrants during the 17th century. Over succeeding centuries, many immigrants to the United States entered the country through the Megalopolis region, with a large percentage deciding to settle in the area. As a result, the population displays a remarkable ethnic and racial mix. The region’s cities have many distinct ethnic neighborhoods, but at the same time immigrants continuously blend into the mainstream culture of the United States, adapting their customs to U.S. society and contributing aspects of their own heritage to the patchwork of U.S. culture.

The population of Megalopolis is highly urbanized. About 1,000 locations in the region are classified as urban by the U.S. Census Bureau. More than 90 percent of the population lives in urban areas, a percentage that is increasing as suburban development fills the spaces between cities. Several very large metropolitan areas dominate the region, including New York City (1997 estimate, 8.6 million); Philadelphia, Pennsylvania (1997 estimate, 4.9 million); Washington, D.C. (1997 estimate, 4.6 million); and Boston, Massachusetts (1997 estimate, 5.8 million).

The region has a high population density, with more than 350 persons per sq km (900 per sq mi). Density ranges from low in rural Virginia to more than 30,900 persons per sq km (about 80,000 per sq mi) on Manhattan Island in New York City. Megalopolis has a high population growth rate as well, adding continuously to the 45 million people, or one-sixth of the nation’s citizens, who live in this region.


Megalopolis is a region of extensive urban metropolitan areas, many of which are located a relatively short distance from each other. New York City, the nation’s largest city, is located here, as is Washington, D.C, the seat of government in the United States. Other major urban areas focus around Boston, Philadelphia, and Baltimore, Maryland.

The Atlantic Northeast

In great contrast to the highly urbanized character of Megalopolis, the Atlantic Northeast is mainly rural in character. It includes the less-populated, less-developed parts of northern New England and upper New York state. The southern boundary of this region skirts the northern edge of Megalopolis just north of the urbanized areas of Portland, Maine, the Merrimack Valley in New Hampshire, the small cities of western Massachusetts, and the Mohawk Valley of New York. On the west and north, the region is bounded by Canada. The Atlantic Ocean forms the eastern boundary.

The Atlantic Northeast is a land of bare rock, thin soils, rugged coastlines, swift streams, and slow-growing forests. Because of its location away from the highly populated and economically active urban core, this region developed its own unique way of life characterized by a high degree of self-reliance. Often families live in the same community for generations. Many communities celebrate local holidays that date to colonial times. In addition, unlike more urbanized regions of the nation, the presence of the forest and the sea continue to have a direct influence on people’s lives. In rural areas, the house of the nearest neighbor is often beyond sight and sound, while the most dramatic presence is that of undeveloped natural environment.

Natural Features

Natural forces have contributed greatly to the present-day geography of this region. For example, mountains and hills consisting of hard crystalline rock were scoured by ice sheets that receded from the region 10,000 years ago. When the ice receded, it left thin soils and an undulating surface favorable for fast-running streams and bright, clear lakes. In Vermont, the rounded summits of the Green Mountains are more pronounced in slope, reaching elevations of nearly 1,900 m (6,300 ft). The Maine coastline is rugged and deeply indented with river channels that are often flooded by the sea.

The landscape is covered with a relatively dense mixed forest of coniferous and deciduous trees. The original trees were cut down for lumber, shipbuilding, and fuel, or were cleared for agriculture. Virtually all of the remaining trees are second-growth. Second-growth trees are usually a less desirable variety because they produce less wood and wood of a lower quality than old-growth trees.


As a region with limited resources, poor soils, and a location distant from the main flow of U.S. commercial activity, the economy of the region is very restricted and offers limited employment opportunities. A harsh climate, thin soils, and a short growing season rule out most cultivated crops. Some corn is grown, but the main rural economy depends on dairy and poultry farms. The timber industry is a mere fraction of what it once was. Commercial fishing, once important to the region, has lagged in recent years. Overfishing has severely depleted the stock. Cod and lobster are, by far, the most important catch. Tourism has become more important in the economy of northern New England. Second homes, weekend cabins, and lake properties are signs of the influx of urbanites from the south.


There are no large cities in the region. Urban centers include Bangor, Maine; Burlington, Vermont; and Glens Falls, New York. The region prides itself on its small hamlets and villages. The Atlantic Northeast has consistently experienced one of the slowest population growths in the nation. It had an overall population density of fewer than 4 persons per sq km (fewer than 10 per sq mi) in the late 1990s. Almost two-thirds of the populace live in a few moderately sized urban centers, largely port cities. The limited regional growth that has occurred took place as urbanites from the crowded Megalopolis area became increasingly attracted to the rural qualities the Atlantic Northeast. Many of these new arrivals often settled in small communities along the southern edges of the Atlantic Northeast, but commuted to jobs in Megalopolis.

The Appalachians and the Ozarks

Separated by several hundred miles, these two mountainous geographic areas are quite similar. The Appalachians border the eastern coastal plain, and the Ozarks lie mainly in Missouri and Arkansas.

These two regions of hill-and-mountain country have similar physical and cultural characteristics. Although there are geological differences between the Appalachian and Ozark areas, both are dominated by steep slopes and narrow valleys. As a result, towns and cities compete with highways, railroads, industrial and commercial enterprises, and fast-moving streams for the small amount of flat land. In addition, both Appalachia and the Ozarks have a history of depressed economic conditions and are sparsely populated. Whether as farmers or miners, industrial workers, or commercial employees in small towns and cities, people struggle continuously to improve their living conditions.

Natural Features

The Appalachian Region consists of highlands running from the mountains of west-central New York in the north to central Alabama in the south. It includes the Appalachian Mountains and a number of surrounding features. The mountains lie roughly parallel to the Atlantic Coast and rise from the Coastal Plain, a flat, low-lying area that stretches along the East Coast from southern Maine to Texas. Between the coastal plain and the mountains is the Piedmont, an area of rolling foothills. To the west of the Appalachians is the Appalachian Plateau, an area of hilly uplands that extends from Pennsylvania to Alabama and descends gradually to the lowlands of the central United States.

The Appalachian Region terminates in the south at the edge of the coastal plain. The northeastern boundary of the Appalachian region lies along the western edge of Megalopolis where urban land use changes to rural land use. The eastern edge follows the change in topography between the rolling uplands of the Southern Piedmont and the Blue Ridge Mountains (the highest range of the Appalachians). To the west, the boundary runs along the western edge of the Appalachian Plateau.

The Appalachian area consists of four distinct landform regions: the Northern Piedmont, the Blue Ridge-Great Smoky Mountains, the Ridge and Valley section, and the Appalachian Plateau. The Northern Piedmont is a gently undulating surface on the inland section of the coastal plain. It reaches only a few hundred feet above sea level at its highest elevations. The western portion of the Northern Piedmont contains productive soils that are fine agricultural lands.

The Blue Ridge is made up of igneous and metamorphic crystalline rocks and includes the highest mountains in the eastern United States. In North Carolina, Mount Mitchell, in the Great Smoky Mountains, is the highest point in the region at 2,037 m (6,684 ft) above sea level. Because of heavy rainfall and warm temperatures, the Blue Ridge area is covered with an impressive forest. The ridges vary in shape and size, but the valleys are mostly flat, narrow, and cleared for agriculture.

Just west of the Blue Ridge is the Great Valley, a natural lowland route running northeast-southwest. The valley is known locally as the Cumberland Valley and the Shenandoah Valley. To the west of the valley, the Appalachian Plateau is chiefly hill country.

The Ozarks include two geographic areas: the Ouachita Mountains and Valleys, and the Ozark Plateau. Together, they represent the only large area of rugged topography between the Appalachians and the Rockies. The rugged Boston Mountains constitute the highest section of the Ozark Plateau. The mountains reach a maximum elevation of more than 850 m (more than 2,800 ft) near Pettigrew, Arkansas. Several popular recreation spots, including Devil’s Den State Park, are located in the Boston Mountains. Oak and pine forests cover the Ouachita Mountains, which stretch about 360 km (about 220 mi) between Little Rock, Arkansas, on the east end to Atoka, Oklahoma, on the west.


Historically, the economy of the region has been depressed. In many parts, natural resources were meager, and agricultural land was scarce and often rocky or hilly. In addition, in some areas, industry was isolated from markets by poor transportation networks. In the 20th century, employment in coal mining, which had brought prosperity to parts of this region, declined.

The depressed economy of Appalachia was one consideration in the creation of the Tennessee Valley Authority (TVA) project in the mid-1930s. TVA built dams, created reservoirs, and improved river navigation. TVA’s work decreased flooding and erosion. Its facilities provided electric power, creating jobs by allowing industries and businesses to locate in much of Appalachia. The TVA helped Appalachia’s economy, but until the 1970s, the region was still synonymous with poverty, depressed living conditions, poor education, and little hope for change.

In the 1990s, the region’s economy has benefited from government facilities such as a center for research on nuclear energy and environmental management at Oak Ridge, Tennessee. Such facilities have stimulated employment opportunities in manufacturing and recreational services, generating pockets of prosperity.

Another spur to growth at the close of the 20th century was tourism. Both Appalachia and the Ozarks contain spectacular scenery and pristine wilderness areas. The Pennsylvania Piedmont and the Shenandoah Valley, treasure troves of American Civil War (1861-1865) history, have drawn sightseers from all over the world. In addition, specialized economic activities have recently helped boost prosperity in parts of the Ozarks. Branson, Missouri has become a country music haven with big hotels and concert halls, while the Ozark-Ouachita uplands have recently experienced a surge of development as a resort and recreation area.

In the agricultural sector, specialized crops have done well. Tobacco farms in the Appalachian valleys and dairy and apple farms in the Ozarks have increased in importance, while lumber milling can still be found in almost every county in both areas.

At the close of the 20th century, urban growth patterns, agricultural specialization, and diversified economies have developed in the Appalachian and Ozarks regions. Because of its scarce resources, the economy in the Appalachians and the Ozarks will probably never be dynamic and expansive. Businesses will have to capitalize on the region’s few strong points, including a pleasant environment, extraordinary mountain scenery, low living costs, outdoor recreational activities, and desirable retirement accommodations.


Cities throughout both the Appalachian and Ozark regions are few and, except for Pittsburgh, Pennsylvania, they are not very large. For decades, people moved out of this region in large numbers, and the total population declined. However, this trend seems to be reversing in many sections. In southwestern Appalachia (Kentucky, Tennessee, and Alabama) and in the Ozarks, the population in the late 1990s was growing, and statistics suggest that the growth trend is likely to continue.

Pittsburgh is the most important urban area in the Appalachian region and has made the transition from a steel center to a modern service and commercial hub. Smaller cities include Scranton, Reading, Lancaster, York, and Harrisburg in Pennsylvania; Huntington, West Virginia; Ashland, Kentucky; and Chattanooga and Knoxville in Tennessee. Most have a diversified industrial and regional service economy. Larger communities in the Ozarks include Springfield and Columbia in Missouri, and Fort Smith and Fayetteville in Arkansas.

The Southeastern Coast

The Southeastern Coast region is a narrow strip along the coasts of the Atlantic Ocean and the Gulf of Mexico. The region begins in the Great Dismal Swamp of southeastern coastal Virginia, extends along the Atlantic Ocean and the Gulf of Mexico, and ends along the sandy beaches of Padre Island, Texas, at the border with Mexico. The coastal lowlands of Virginia, North Carolina, South Carolina, Georgia, Florida, Alabama, Mississippi, Louisiana, and Texas are included. The inland boundary of the Southeastern Coast is a transition zone that separates poorly drained coastal lowlands from better-drained areas inward.

The Southeastern Coast region is dynamic, with a range of both traditional and modern characteristics in its culture and economy. Burgeoning cities and factories are found here, as well as rural seaside villages and towns.

Natural Features

The Southeastern Coast is a land of gentle slopes, poor drainage, and fragile environment. Except in Florida, sediments of marine origin underlie almost the entire region. These sedimentary beds extend into the sea as part of the Continental Shelf, the gently sloping edge of the continent covered by seawater. The peninsula of Florida is a recently-emerged mass of carbonate rocks, largely limestone. It is characterized by an immense area of inadequate drainage in the south and by underground streams, sinkholes, and pits in the north. Below the surface, limestone formations contain caverns. Most are water-filled. Sometimes the fragile roof of a cavern collapses, creating sinkholes that soon fill with water to become small lakes.

Many great rivers empty into the sea in this region, including the Mississippi and Río Grande rivers. At the mouths of these rivers is a rich mixture of inland silt, fresh water, and sea water, which provides an ecological niche that supports a remarkable range of birds, reptiles, fish, and mammals, as well as distinctive plant life. Natural features include the shallow, sluggish waterways of the Everglades and Lake Okeechobee in Florida, the Okefenokee Swamp on the Georgia-Florida border, and the bayous of the Mississippi delta.

Along the Southeastern Coast, human activities—industry, construction, and mining—have often damaged wetlands and caused ecological problems. This region has seen confrontations between developers and preservationists over a number of issues. The effects of pesticides are heatedly debated in southern Louisiana. In southern Florida, the future of the Everglades, a vast marsh, remains unresolved because much of the water that formerly drained into the marsh is being diverted for agricultural irrigation and household use.

The region’s natural features and geography are closely connected to its economic development. Poor drainage and poor soils are problems for agriculture, but these are partially offset by the advantages of a long growing season and adequate moisture. These advantages allow growing of subtropical, off-season specialty crops, such as vegetables and citrus fruits. The growing season of this region is typically more than 320 days a year. Productive agriculture, much of it subtropical, thrives. Crops include rice, sugarcane, citrus fruits, cotton, and grain sorghum. Beef cattle are grazed in the region. The nearness of the ocean provides ports for shipping and supports a fishing industry. The ocean, beaches, and a warm climate also support the tourist industry.


Mineral production along the Southeastern Coast is substantial, with oil and natural gas leading the way. Much of the production is offshore, with wells drilled into the Continental Shelf. Salt domes—underground geological formations that trap deposits of petroleum, natural gas, and sulfur—are widespread in the ‘tidelands,” as the shelf is called. Huge quantities of phosphates (used for fertilizers) are mined, as well as salt and sulfur. Extraction of minerals such as phosphate rock, salt, sulfur, petroleum, and natural gas contributes greatly to the economy.

The economy of the Southeast coastal region benefits from the Intracoastal Waterway , a series of canals and protected water routes extending for about 1,740 km (about 1,080 mi) along the Atlantic Coast and for about 1,770 km (about 1,100 mi) along the Gulf of Mexico coast. Because of modest depth, the waterway is used primarily by barges and small boats. Two-thirds of its traffic is concentrated on the section between Houston, Texas, and the Mississippi River. Key commodities include oil, grain, cotton, sulfur, and petrochemicals. The waterway connects with the Mississippi River system, allowing barge traffic to travel far inland to the extremities of the Mississippi navigational system.

New Orleans, Louisiana, has developed its legacy as a former French colony into a world-renowned tourist destination. In addition, it has used its location at the mouth of the Mississippi River to develop a major port, particularly for trade between the United States and Latin America. Other ports in the region include Mobile, Alabama; Pensacola, Tampa, Miami, and Jacksonville in Florida; and Galveston and Corpus Christi, in Texas.


The present population of the region is 38 million. In particular, the population of Florida has grown spectacularly. Florida’s population in 1990 was 12,937,926, more than 13 times the size of its 1920 population of 968,470. In the ten years after 1980, when 9,746,961 people lived there, Florida’s population increased by 32.7 percent.

Major cities in the region include Miami, Florida; New Orleans, Louisiana; and Houston, Texas. Urban areas, especially the larger ones, are significant destinations for migrants, particularly by people from outside the region. Cotton and oil production contributed to Houston’s growth, from a population of 1,595,138 in 1980 to an estimated population of 5,539,949 in 2006. Today, Houston is a diversified industrial center and a world leader in the petrochemical industry.

The cities of Florida have absorbed most of the state’s rapid population growth. Miami has grown, to a large extent, because of migration from Cuba after a communist government was established in Cuba in the early 1960s (see Cuban Americans). Orlando has grown explosively as a convention and tourist center. Jacksonville, Tampa, and Fort Lauderdale have swelled from migration of retirees from northern states. Smaller Florida cities, such as Destin, a weekend resort location, and West Palm Beach, a winter resort and tourist haven, have also experienced stunning growth.

The Inland South

The Inland South is a transition zone between the Southeastern Coast and the Heartland. It occupies much of the coastal plain surrounding the southern sections of the Appalachians and Ozarks. Portions of Texas, Louisiana, Arkansas, Tennessee, Mississippi, Alabama, Georgia, North Carolina, South Carolina, and Virginia are included.

The Inland South has certain economic, demographic, and political characteristics that bestow regional uniqueness. The economy of the region was originally based on slave labor and on the large-scale production of crops, particularly cotton. In most parts of the region, manufacturing replaced agriculture as the primary source of income during the second half of the 20th century. As a legacy of slavery, both rural and urban areas have a mix of black and white populations. The region remains for the most part politically conservative. This combination of black and white populations and conservative political values helps to distinguish the Inland South as a distinctive region.

Natural Features

The region consists of rolling plains and hills covered by grassland and mixed forest. It includes the foothills of the Appalachians and the hill lands south of the Ozark plateau and the Ouachita Mountains. Elevations range from 50 feet in the south to 600 feet in the east, west, and north. The underlying rocks near the coast consist of unconsolidated sediments, while the interior has a section of older, crystalline rocks.

Soils of moderate fertility support a fast-growing cover of mainly coniferous trees, such as the southern pine, which is able to reach full growth in 20 years. In some areas, such as the Black Belt of Alabama and Mississippi and the Black Waxy Prairie of central Texas, deep, dark, naturally fertile soils support productive agriculture. Alluvial soils, which are deposited by the area’s many large rivers, are also dark, rich in nutrients, and highly productive.


Agriculture has long been a major part of the region’s economy. Cotton cultivation was a catalyst for settlement in the 19th century, when large cotton plantations developed. These plantations had a long-lasting effect on the make-up of society in the Inland South. About 70 percent of the population is white and 28 percent is African American, mainly descendants of slaves originally brought from Africa to work the plantations.

During the 20th century, the rural economy diversified enormously with substantial acreage devoted to soybeans, corn, beef cattle, poultry, rice, and peanuts. Cotton is still important, particularly in the Mississippi lowland. Tobacco dominates the gentle slopes on the coastal plain of Virginia, North Carolina, and South Carolina.

Oil and natural gas have historically played a strong role in the region’s economy, particularly in the states of Texas and Louisiana. Manufacturing has also increased in importance. During the last half of the century, many manufacturing facilities formerly located in the Heartland and Megalopolis have relocated to the South. Many of these companies moved to the Inland South to take advantage of the lower wages and the lack of strong labor unions in the region. Since 1947, the South’s share of the nation’s manufacturing workers has increased significantly.


In the early 1990s, estimates indicated that about 40 million people were living in the Inland South region. This population, concentrated primarily in urban areas, is about 70 percent white and 28 percent black. The population density varies from fewer than 4 persons per sq km (about 10 per sq mi) in the less populated rural areas to more than 190 per sq km (more than 500 per sq mi) in the region’s largest cities.

The major urban areas of the Inland South are Atlanta, Georgia, and Houston, Texas. Atlanta is the business center of the southeastern United States. It is a major center for national conventions and trade. Houston is the fourth largest city in the United States. It serves as a major financial, distribution, and manufacturing center for the South. These two regional economic centers were growing at a rapid rate in the late 1990s, as the industrial and economic base of the Inland South strengthened and more people migrated from other areas of the country.

The Inland South is also home to a number of the nation’s fastest growing medium-sized metropolitan centers, including Memphis, Tennessee; Fort Worth, Texas; and Birmingham, Alabama. Tremendous population growth occurred in the 1990s in the highly industrialized district of North Carolina, which includes the cities of Charlotte, Winston-Salem, and Greensboro. This area attracted large numbers of people to jobs in high-technology and manufacturing industries.

The Heartland

The Heartland extends eastward along the southern shores of lakes Erie and Ontario and along the western slopes of the Appalachian Plateau. To the south, there is a transition to the Inland South and the Ozark-Appalachian region. The boundary to the west is also a transition zone, where Heartland cornfields give way to the vast wheat fields of the Great Plains. In the north, the boundary merges into the Northern Forest region of the Great Lakes. The Heartland includes southern Wisconsin, lower Michigan, Illinois, Indiana, most of Ohio except for its far eastern part, Iowa, northern Missouri, far eastern South Dakota, Nebraska, Kansas, and parts of Tennessee and Kentucky.

The Heartland has the largest population and the most economic output of any U.S. region. It is the most extensive area of highly productive farmland in the United States, as well as the industrial core of the continent.

Natural Features

Almost all of the Heartland is in the vast central lowland of North America. The land is mostly level with some gently rolling hills. Horizontal sedimentary strata of limestone, sandstone, shale, and dolomite underlie the entire region. The gentle slopes of the region result mainly from glacial action during the Pleistocene Epoch (1.6 million to 10,000 years ago). The flatlands and productive soils were produced during the last Ice Age at the close of the Pleistocene Epoch, as were the Great Lakes, which were formed by glacial scouring and then filled with the melt water of retreating glaciers. Almost all of the surface water in the Heartland drains into the river systems that feed the Mississippi River, and flooding is a natural hazard in the spring. Both the Great Lakes and the Mississippi have long served as vital transportation links that contribute to the economy of the region.


The Heartland has a varied economy that underwent a major transformation late in the 20th century. The region possesses the largest area of highly productive farmland in North America. Industry also plays a major role in the region.

For more than a century, the Heartland supported a thriving center of manufacturing. Since the 1970s, manufacturing has declined. By the end of the 20th century, the economic sector generating the most revenue was the service sector, including commerce and trade. Despite the increase in service industry jobs, the Heartland remains the agricultural and industrial center of the nation.

Both industry and agriculture benefit from an extensive waterway system that includes the Great Lakes and the drainage basins of the Mississippi, Missouri, and Ohio rivers. Navigation is improved by hundreds of canals, locks, and dams, which also improve flood control and generate hydroelectricity. Water transportation moves millions of tons of iron ore and coal to steel mills and other heavy industries. In addition, the relatively level terrain has facilitated construction of a dense network of highways and railroads.

Agriculture continues to be a major economic force in the region. Rich, deep soils and plentiful rain, complemented by a sunny, hot growing season, give rise to vast and productive croplands specializing in corn, soybeans, alfalfa, hay, and fruits such as apples and cherries. The livestock industry is widespread in the region, with huge feedlot operations supporting cattle production in the west. Hogs, found mainly in Iowa and Illinois, are raised with corn and soybeans. Dairy cattle are found throughout the northern part of the region, particularly in the southern Wisconsin Dairy Belt, famous for its milk, cheese, and butter production.

For more than a century, the U.S. manufacturing belt—including Illinois, Indiana, Ohio, western Pennsylvania, western New York, southern Michigan, and southern Wisconsin—served as one of the great industrial areas of the world. By 1980 the region’s industrial dominance began to wane, challenged by vigorous industrial growth in the South and West and by the decline of manufacturing in favor of service industries. In the last three decades of the 20th century, the region’s share of North American factory production declined significantly.

Although industrial jobs have been leaving the Heartland, the region’s industrial districts are still important. Today, auto assembly is important in Cleveland, Ohio. Tire and rubber manufacturing continue in Akron, Ohio. The automobile industry is important in southern Michigan, particularly in Detroit, Flint, Pontiac, Ann Arbor, Ypsilanti, and Lansing, as well as in Toledo, Ohio.

Centers of heavy manufacturing include Chicago, Illinois; Gary, Indiana; and Milwaukee, Wisconsin. The steel industry is still important in the Chicago-Gary region, though much business was lost to competition from Asian steel producers during the closing decades of the 20th century. Indiana and Ohio have diversified industry with factories producing secondary automotive products such as batteries, radios, and automotive transmissions. The middle Ohio River, an 800-km (500-mi) stretch of the Ohio River valley, has been a major center of heavy manufacturing, benefiting from large supplies of industrial coal from western Pennsylvania and West Virginia and from low cost river transportation. Examples of heavy manufacturing in this area include iron and steel, metal products, and fabricated metals and machinery, such as motor vehicle manufacturing and assembly.

In the western section of the Heartland, St. Louis, Missouri, located at the confluence of the Missouri and Mississippi rivers, is a center of diversified industry, with an emphasis on aircraft manufacturing and automotive assembly. The western Heartland also includes major food processing industries in cities such as Des Moines, Iowa; Omaha, Nebraska; Kansas City, Missouri; Council Bluffs, Iowa; and Lincoln, Nebraska.


As the largest productive agricultural region and the industrial nucleus of the United States, the Heartland contains the largest population of any region of the nation. Population density varied dramatically throughout the region during the 1990s, from fewer than 4 persons per sq km (about 10 per sq mi) in rural areas to more than 4,642 per sq km (more than 12,024 per sq mi) in the heart of Chicago. The vast majority of the population is concentrated in the many urban areas that developed around manufacturing centers. A decline in manufacturing jobs since the 1970s slowed the rate of expansion in many urban areas, but these cities continued to grow as people chose urban living over rural lifestyles.

Large cities in the region include Chicago, Illinois; Milwaukee, Wisconsin; Detroit, Michigan; St. Louis and Kansas City in Missouri; Indianapolis, Indiana; and Cleveland, Ohio. Chicago is the dominant metropolis. It serves as a wholesale center and transportation hub for the region. St. Louis is a commercial and transportation hub that is the largest urban center between Chicago and the Pacific Coast. Other major cities include Milwaukee, Wisconsin; Detroit, Michigan; and Minneapolis and Saint Paul in Minnesota. Urban expansion continues, although it slowed toward the end of the 20th century, as the region lost population to the South and West.

The Northern Forests

While the physical characteristics of the Northern Forests region extend through much of central Canada and Alaska, the portion that lies within the contiguous United States is limited to the upper Great Lakes area. This region includes much of northeastern Minnesota as well as northern Wisconsin and Michigan.

The common characteristics that make the Northern Forests a distinctive region are its vast forests and its abundant rivers and lakes. The region’s economy focuses on the export of a few primary products via the shipping routes of the Great Lakes.

Natural Features

The Canadian Shield, a vast, gently rolling surface made up of granitic rocks, underlies the eastern two-thirds of the region. During the Pleistocene Epoch, ice sheets scoured the land, remolding the surface and removing most of the existing soil to expose bare rock and rounded hills almost devoid of soil. To the west of the shield is a large, broad lowland that is underlain by softer sedimentary materials, deposited by rivers flowing across the Rocky Mountains and the Canadian Shield.


The natural environment has dominated the economic development of the region. In most areas, the economy is based on a single commercial activity. The primary source of income derives from the transportation of iron ore and minerals on the waterway system. Lake Superior, northern Lake Michigan, and northern Lake Huron as well as thousands of small lakes and rivers provide major water transport routes in this area. Logging, pulpwood production, and fishing are important activities in many communities. The region suffered from economic stagnation in the last decades of the 20th century.


The Northern Forest region is an area of low population density, with fewer than 4 persons per sq km (less than 10 per sq mi) in most of the region. Less than 2 percent of the U.S. population lives in this area. Overall there has been a net loss of population as people moved out of the region. The few small urban centers include Duluth, Minnesota; Superior and Ashland in Wisconsin; and Marquette and Sault Sainte Marie in Michigan. These are all port cities that function as principal hubs for water and land transportation routes from the upper Great Lakes area.

The Great Plains

The Great Plains region is a vast area stretching from Canada in the north to Mexico in the south. The frontal ranges of the Rocky Mountains define the region’s boundary to the west. To the east, the boundary is the transition zone stretching from southern Texas and eastern Oklahoma in the south to the western reaches of Minnesota in the north, where large-scale wheat production gives way to the corn-hog-soybean and general farming complex of the Heartland.

The Great Plains region is known for its extensive farming and ranching; fertile soils; production of minerals such as coal, petroleum, and natural gas; and dramatic variations in climate. Although periodic droughts do occur on the Great Plains, water is extensive in many areas, with rivers originating in the Rocky Mountains and flowing eastward to connect with the Mississippi drainage system or the Gulf of Mexico.

Natural Features

The landscape is characterized by flat to gently sloping land, with elevations of 1,500 to 1,800 m (5,000 to 6,000 ft) in the west, sloping gradually to elevations of 500 m (1,500 ft) in the east. Sedimentary strata underlie most of the region. Although much of the Great Plains is relatively flat, several interesting geographical features dot the landscape. They include the Hill Country of Central Texas, the deep cut Palo Duro Canyon of the Texas Panhandle, the Flint Hills of Kansas, the Nebraska Sand Hills, the Black Hills of South Dakota and Wyoming, and the dramatic and highly eroded Badlands of the Dakotas and Nebraska.


Vast wheat farms, using large-scale machinery, dominate the northern plains landscape. The winter wheat belt centers on Kansas, while spring wheat dominates in the Dakotas. Other important grain crops include sorghum, barley, and rye. In the south, irrigated acreage and mild climate conditions allow for the cultivation of cotton, onions, spinach, and peanuts. Further north, irrigation favors cantaloupes and sugar beets in the area around Greeley, Colorado. Cattle ranching is another important economic activity.

Mineral production in the Great Plains is substantial. Oil and natural gas are produced in Texas and parts of Oklahoma and Kansas. Coal has become important in Wyoming, Montana, and the Dakotas. In these states, vast open-pit mines produce coal with low sulfur content, a cleaner-burning variety much preferred for generating electricity. In the Powder River Basin in north central Wyoming and southern Montana, mining operations have grown rapidly and been accompanied by the growth of related settlements. Each day, dozens of long, coal-laden trains pull out of the area, headed to electricity-generating plants throughout the United States.


In the 1990s approximately 70 percent of the population of the Great Plains lived in scattered urban areas. Denver, Colorado is by far the largest city of the region, with a metropolitan population of 1.9 million people in 1997. It lies along the western boundary of the region. Denver is a diversified city, serving as a market and industrial center for both the Rocky Mountain region to the west and the Great Plains. Other large urban centers include San Antonio, Texas; Tulsa, Oklahoma; and Wichita, Kansas. These cities serve as regional trading centers for surrounding areas.

The Rocky Mountains

The Rocky Mountains region can be characterized as an area of breathtaking scenery, rugged terrain, scanty resources, and scattered population. The boundaries of this region are fairly precise, as the sharp relief of the frontal ranges contrasts with the relatively flat Great Plains region to the east. To the west, the Rocky Mountains region is bordered by the plateaus and basins of the Intermontane region. The northern boundary of the U.S. Rockies is considered the Canadian border, although the mountains physically stretch well into Alberta and British Columbia. In the south, the mountain range ends north of Albuquerque, near Santa Fe, New Mexico.

Natural Features

The Rocky Mountains were formed relatively recently in geologic time. During the Cretaceous Period, from approximately 135 million to 65 million years ago, a saltwater extension of the Gulf of Mexico covered most of this region, as well as the Great Plains. A deep layer of sediment, perhaps as much as 6,000 m (20,000 ft) thick, covered the granitic rocks that now form the Rocky Mountains. Finally, a series of crustal uplifts, accompanied by large-scale erosion, created the mountainous terrain that exists in the region today. .

These block-faulted mountains are young compared with many of the world’s other mountains. They are characterized by a complex system of troughs and ridges that are a result of tectonic uplift and subsidence of adjacent blocks of the earth’s crust. Other features of the area’s landscape have been shaped through glaciation. Many of the major rivers of the western United States, including the Columbia, Fraser, Missouri, Colorado, Arkansas, Rio Grande, and Snake, originate in the upper elevations of the Rocky Mountains.


Although irrigated farming, livestock ranching, and lumbering offer limited economic opportunities within the region, the two major commercial activities in the Rocky Mountains are mining and tourism. Small mines are scattered throughout this region, but several have achieved major significance at one time or another. Major finds of gold, lead, zinc, and silver were discovered around Leadville, Colorado, particularly in the last quarter of the 19th century. Today, Leadville continues to be a mining center and is the home of the Climax mine, which employs over 3,000 workers. This mine is the world’s largest producer of molybdenum, which has a very high melting point and is used to make the heat-resistant steels used in automobiles, aircraft, and various commercial and industrial appliances. The Coeur d’Alene area of northern Idaho also continues to be a productive mining center, producing substantial quantities of silver, lead, and zinc.

Tourism is based on abundant natural attractions and outdoor recreation and has become the most vigorous part of the region’s economy. Resort communities have been established to cater to the region’s tourist industry, and their population often grows exponentially during peak tourist seasons. Skiing is the dominant winter season activity. Major destinations are Aspen, Vail, Keystone, Breckenridge, and Copper Mountain in Colorado, as well as Sun Valley in Idaho and Snowbird in Utah. In the summer, tourists flood the region to visit points of interest, such as Pikes Peak, Royal Gorge, Rocky Mountain National Park, Yellowstone National Park, Grand Teton National Park, and Glacier National Park.


There has been little urban development in the Rocky Mountains. Throughout history, the population of the area has been very sparse. Many of the permanent settlements are tied to economic activities such as tourism, forestry, mining, and agriculture. Populations in these locations often vary with economic conditions. For instance, the number of people living in some communities often fluctuates with changes in mining productivity or according to seasonal cycles of employment in the tourism industry. In the late 1990s there were fewer than 4 persons per sq km (10 people per sq mi) and few cities within the area have populations greater than 50,000 people. The one city that exerts the most influence within the region is Denver, Colorado, which is not actually located within the region, but lies at its eastern edge. Denver serves as a commercial, industrial, and distributing center for the Great Plains as well as the Rocky Mountains.

The Intermontane Basins and Plateaus

The Intermontane Basins and Plateaus region is flanked on the west by the major Pacific coastal mountain ranges and on the east by the Rocky Mountains. In broad terms, the region consists of three distinctive subregions. The extensive Colorado Plateau encompasses parts of Colorado, Utah, Arizona, and New Mexico. The Columbia Plateau occupies eastern Washington, eastern Oregon, and southern Idaho. And the vast basin and range country lies between and around these two dominant plateau areas.

The Intermontane region is characterized by sparse population concentrated in a few major urban centers, a relatively isolated setting between extensive mountainous areas, varied topography, arid and semi-arid climate patterns, limited water assets, and considerable mineral resources.

Natural Features

The geologic history within the Intermontane region varies by subregion. Basaltic lava covered the Columbia Plateau before a significant network of lakes deposited layers of silt. Faulting and warping created the present-day rugged and varied landscape. The Colorado Plateau features high plateaus and mesas dissected by extensive, steep-sided canyons. The remainder of the region consists of basin and range country, in which mountain ranges alternate with relatively flat basins. The mountain ranges are distinguished by block faulting, which gives them a rough, rectangular shape. The basins are characterized by features such as alluvial fans (soil or mineral deposits left by mountain streams that encountered flat terrain) and salt lakes. Perhaps the best known of these lakes is the Great Salt Lake.


The region’s economy is based on irrigated farming, livestock grazing, mining, and tourism. The most critical resource for this region is water. Water for irrigation comes from the main rivers or from wells dug into aquifers (natural underground water reservoirs). Despite limited water resources, this region contains a number of major river basins, including the Colorado, Snake, Salt, Columbia, and the Rio Grande. The water of these rivers is used intensively. For example, the water of the Colorado River is so fully utilized for irrigation and urban uses that most of it does not reach its mouth in the Gulf of California. Irrigation in this region supports a variety of crops, including potatoes, apples, cotton, sugar beets, peaches, and cherries. Hay and grains are produced, often to support a scattered livestock trade that includes cattle, sheep, and goats.

Principal minerals found in the Intermontane Region include coal, petroleum, and copper. The open-pit mine at Bingham Canyon, Utah, is the largest copper mine in the world, contributing to the U.S. position as the world’s second largest copper producer, after Chile.

Tourism is also important for this region, which attracts people from all over the world. Dramatic scenery is provided by the highly differentiated landscape, exemplified by the Grand Canyon, Bryce Canyon, Zion Canyon, Mesa Verde, the Petrified Forest, Death Valley, the Wasatch Mountains, and the Great Salt Lake.


This Intermontane region has great cultural diversity. The Rocky Mountains are home to approximately 300,000 Native Americans, descendants of the original inhabitants. While Native Americans can be found in all states of the Intermontane region, they are concentrated in the Four Corners area of Colorado, Utah, New Mexico, and Arizona. This area is dominated by the vast Navajo Indian Reservation; the Hopi Indian Reservation also lies within its boundaries (see Navajo (People); Hopi).

The first European inhabitants of the area were the Spanish, who surveyed the region in search of mineral wealth. Southern areas—the states of Arizona, New Mexico, and Texas—border on Mexico and have large Hispanic populations. Street names, foods, and annual celebrations attest to strong historical links to Mexico. Many members of the Church of Jesus Christ of Latter-day Saints (commonly referred to as Mormons) live in Salt Lake City, Utah, and the church’s sphere of influence covers a much broader area. In the mid-1800s, Mormon farmers migrated to the area around Salt Lake City in search of an isolated area where they could practice their religion in peace. The rush to find gold and other precious minerals prompted sporadic movement into the area later in the 1800s.

In general, the Intermontane Basins and Plateaus region is sparsely populated with few significant urban centers. In the 1990s, the overall rate of population growth in the region was high, particularly in the southern regions, as people were increasingly attracted to the mild winters, recreational opportunities, healthful climate, and year-round sunshine. The region has a high immigration rate, both legal and illegal, of citizens from Mexico who move into its southern margins (see Mexican Americans). Border communities have swelled as millions of Hispanics crossed the border to settle in the region.

Historically, the population has remained scattered throughout the region until the last half of the 20th century, when many regional urban centers grew rapidly. The cities in the southern part have grown particularly quickly as increasing numbers of people are attracted to the dry, warm desert environment. Between 1960 and 1990, the metropolitan population of Las Vegas, Nevada, increased by six times, and that of Phoenix, Arizona, tripled. During the same time period, populations doubled in the metropolitan areas of Albuquerque, New Mexico; El Paso, Texas; and Tucson, Arizona.

The largest city in the region is Phoenix, Arizona, with a metropolitan population of 2.8 million (1997 estimate). Other urban centers include Salt Lake City, Utah; Tucson, Arizona; Las Vegas, Nevada; El Paso, Texas; and Albuquerque, New Mexico. These cities serve as regional market centers, and some of them also have specialized economies. For example, Las Vegas, one of the fastest growing urban areas in the United States with a population of 1.3 million (1997 estimate), is known for legalized gambling. El Paso, with a metropolitan population of 702,000, is closely connected economically and culturally with the neighboring Mexican border city, Ciudad Juárez. El Paso serves as a gateway and a destination for Hispanic migrants to the United States.

The California Region

This geographic region encompasses most of the settled part of the state of California, including the coastal area stretching from the northern border of Mexico to north of San Francisco. In the north, the region ends at the northern Coast Ranges, the Klamath Mountains, and the southern Cascades. The eastern boundary falls along the edges of the Sierra Nevada mountains and the Peninsular Ranges of Baja California. To the southeast, the region borders the desert lowlands of Death Valley and the Mojave Desert, and the area around the Salton Sea and the Imperial Valley.

Although extremely diverse physically and culturally, this region is generally characterized by productive agriculture, a Mediterranean climate with dry summers and warm, dry winters, extensive urban development, and the presence of high-technology industries.

Natural Features

There are three broad subregions within this area: the coastal mountains, valleys, and plains; the Central Valley; and the Sierra Nevada Mountains. The coastal mountains parallel the coastline and display prominent fault lines, of which the most widely known is the San Andreas. The coastal plain is narrow and heavily populated and includes giant metropolitan areas, specifically San Diego, Los Angeles, San Francisco, and Oakland. The Central Valley consists of a broad trough, 100 to 160 km (60 to 100 mi) wide and more than 720 km (450 mi) long, filled with sediment carried down in runoff from nearby mountains. The valley of the Sacramento River dominates the northern portion, and the San Joaquin River dominates the southern half. The Sierra Nevadas are rugged, fault-block mountains with evidence of glacial erosion, such as the impressive deep-cut valleys of Yosemite National Park.

The California region lies at the convergence of the North American and Pacific tectonic crustal plates. Tectonic plates are large blocks of the earth’s crust that are moving slowly across the surface of the earth. As these plates collide and grind against each other, they generate tremendous energy. See Plate Tectonics. In California, the forces generated by the friction of these plates create an unstable crustal zone that causes severe earthquakes. Major fault lines trend in a northwest to southeast direction and much of the area’s landscape is adorned with fault lines and other characteristic fault features.


The California economy is robust and very diversified. The state leads the nation in agricultural production, relying heavily on irrigation. Principal crops include cotton, hay, citrus fruits, and vegetables. The making of wine is also a major industry. Dairy farming, as well as cattle and chicken production, are also important. Most of these endeavors are supported by irrigation, and aqueducts transfer much of the water from areas that receive more precipitation, such as the slopes of the Sierra Nevada.

In the southern part of the state, the main industries include aircraft manufacturing, oil refining, aerospace technology, electronics, printing and publishing, and the movie and entertainment industry. In the north, the economy is quite different, with an emphasis on high technology, government activities, and insurance and banking services. In both the north and the south, tourism is prominent, and Los Angeles and San Francisco are major convention destinations. In the Central Valley, food processing and transportation are important, with the larger cities serving as regional marketing centers.


Approximately 32 million people live in the California region. California’s population growth has been one of the most impressive stories in the historical development of the United States. People moved to California to take advantage of the mild, Mediterranean climate, the abundant resources, and the promise of prosperity. Growth has been due in part to migration from other states, but also to foreign immigration, some legal and some not. In any case, the region’s population is very diverse. It accounts for more that a third of the nation’s Armenians, Chinese, Filipinos, Iranians, Japanese, Koreans, Mexicans, and Vietnamese.


California is a state of giant cities and urban sprawl. According to the Bureau of the Census, the greater Los Angeles metropolitan statistical area (MSA) is the second largest MSA in the United States, and San Francisco-Oakland-San Jose is the nation’s fifth largest MSA. Other big urban centers include San Diego, Sacramento, and the cities of the Central Valley, including Stockton, Fresno, and Bakersfield.

The Pacific Northwest

The Pacific Northwest region is a strip 300 km (200 mi) wide of mountainous land that stretches along the coastline of northern California, Oregon, and Washington. The southern and eastern boundaries of the region are defined by the Cascade Range, while a series of coastal ranges, including the Coast Ranges, the Klamath Mountains, and the Olympic Mountains, skirt the western boundary along the Pacific coastline. The Canadian border defines the northern boundary of the area, though the geographic characteristics continue northward through Canada into southwestern Alaska. Lying between the coastal ranges and the interior mountains is an inner trough, including the Willamette Valley in Oregon and Puget Sound in Washington.

The region is characterized by spectacular scenery, mountainous terrain, a temperate marine climate with abundant precipitation, significant natural resources, and a population which lives in relative remoteness on the western fringes of the United States, isolated in part by substantial physical barriers.

Natural Features

The Coast Ranges and the Cascade Mountains dominate the terrain of the Pacific Northwest. These two north-south mountain systems run in ridges parallel to the Pacific Coast. Most of the population of the Pacific Northwest lives in the lowlands between these two mountain systems. Another major geographic feature of the Pacific Northwest is the Columbia River, one of the nation’s largest rivers. It cuts through a deep gorge in the Cascade Mountains along the border between Washington and Oregon before crossing lower-elevations of the coastal mountains to empty into the Pacific.

The Cascade Mountains extend almost due north and south across central Washington, Oregon, and northern California. The mountains lie about 160 to 240 km (about 100 to 150 mi) inland from the Pacific Coast. The higher elevations of the Cascades have a continuous snow cover. A number of east-west highways built through passes provide fairly easy travel through these mountains, except in winter, when they are periodically blocked by snow.

The Cascades include a series of volcanic peaks, including Mount Rainier, which rises (4,392 m/14,410 ft), Mount Adams (3,742 m/12,276 ft), and Mount Baker (3,285 m/10,778 ft) in Washington; Mount Hood (3,426 m/11,239 ft) in Oregon; and Mount Shasta at (4,317 m/14,162 ft) in California. Some of these volcanoes are still active, including Mount Saint Helens in Washington(2,550 m/8,365 ft), which erupted violently on May 18, 1980, blowing 400 m (1,300 ft) in elevation from the peak and sending a column of ash as high as 19 km (12 mi) high. In addition, the region experiences periodic mild earthquakes.

To the west of the Cascades lies a depression containing Oregon’s Willamette Valley and Washington’s Puget Sound. In the south end of the depression, the winding Willamette River drains Oregon’s central Willamette Valley before entering the Columbia River at Portland. The lowland depression continues north into Washington, where it submerges beneath Puget Sound, an inland extension of the Pacific Ocean lined with jagged peninsulas. The sound contains more than 300 islands, including the San Juan Islands. The Strait of Juan de Fuca provides shipping access to Puget Sound. The strait cuts west at the northern end of the sound and separates Canada’s Vancouver Island from Washington’s Olympic Peninsula.

To the west, the Olympic Mountains on the Olympic Peninsula are the northernmost of the U.S. Coast Ranges. Because they rise from a dense coniferous forest that lies just above sea level, the Olympics are among the most visually impressive peaks in the United States. They reach a maximum elevation of 2,428 m (7,965 ft) at Mount Olympus. The Coast Ranges continue south through the Oregon Coast Range and the Klamath Mountains before continuing down through California and the Baja California peninsula in northwestern Mexico.


The Pacific Northwest has a large but limited natural resource base, leading to an economy that is not highly diversified. The area’s abundant precipitation and temperate climate support dense, coniferous forests, which are the basis of the region’s dominance in the production of lumber, plywood, particleboard, pulp, and paper. Mountainous terrain and high levels of precipitation have provided this region with an enormous hydroelectric potential, focused on a system of dams and power-generating plants located on the Columbia and Snake rivers.

The mountainous terrain means that little land is suitable for agriculture, and dairy farming and grazing are the primary agrarian activities. Other agricultural activities include the growing of fruits, vegetables, grass seeds, mint, and hardier grain crops. The waters of the Pacific Northwest coast are ranked as one of the major fishing centers of the world. Salmon is the most important fish commercially, but the region has significant catches of herring, halibut, pollack, cod, and shellfish. Additional economic activities in the region include the aerospace industry, shipping, high-technology enterprises, shipbuilding, and the manufacture of wood products.


Regional population has remained relatively low, though two major urban centers have developed in the region. Portland, Oregon, is a dominant commercial center at the mouth of the Columbia River, and Seattle, Washington, is a large urbanized development on the shores of Puget Sound.


The Alaska region includes the entire state of Alaska and encompasses approximately one-sixth of the total landmass of the United States, with about 1,600,000 sq km (about 615,000 sq mi) in area. The region is a sparsely populated area of vast wilderness and spectacular natural beauty, with varieties of animal life that are unique in the United States. Long winters, short summers, and large seasonal fluctuations in the length of days and nights characterize the harsh arctic climate that exists in much of this region. The exception is the narrow area that runs along the southeastern coast, where long, mild, wet winters and short, dry summers predominate.

Natural Features

The topography of the region is extremely varied, with mountainous zones in southern and central Alaska, narrow coastal areas in the southwestern portion, and sweeping coastal plains to the north. The Alaska Range occupies south central Alaska, while the Wrangell Mountains skirt the southeastern Alaskan coastline along the border with Canada. The arctic portion of Alaska is composed largely of flat, featureless coastal plains bounded in part by the massive Brooks Mountain Range.

Conifer forests, often referred to as taiga, dominate Central Alaska, covering relatively flat terrain stretching hundreds of miles. Water, found in countless lakes and in extensive river basins such as the Yukon and Kuskokwim rivers, is abundant in the region.


A few specialized activities dominate the region’s commercial economy, including fishing in the waters off southwestern Alaska, logging activities, reindeer herding on the Seward Peninsula, and extensive oil and gas exploration along Prudhoe Bay, located on the north coast along the Arctic Ocean. Alaska’s North Slope provides one-fifth of all U.S. oil production, ranking second in yield after Texas.


A harsh environment, remote location, and inadequate transportation have kept the population in Alaska small. Historically, the Inuit (often referred to as Eskimos) lived in widely scattered settlements and relied on subsistence activities, such as hunting, fishing, and trapping. More recently, the trend has been toward larger concentrations of settlements. Some 15,000 whites have moved into the region, many of whom are military personnel, government employees, or oil company workers.

Anchorage, the dominant population and economic center in Alaska, contains approximately half of the state’s inhabitants, with a population of 275,043 (2005 estimate). Other large communities include Fairbanks and Juneau, the state capital.


The 2,600-kilometer-long (1,600-mile-long) string of tropical islands, islets, and reefs known as the Hawaiian Islands is the smallest geographic region in the United States, covering a total area of 28,311 sq km (10,931 sq mi). The region is located in the middle of the Pacific Ocean, more than 3,200 km (2,000 mi) southwest of California. The majority of the land area is concentrated on eight islands, with the largest and easternmost island of Hawaii possessing almost twice as much area as the other seven major islands combined.

Hawaii is the only island state of the United States. It has a tropical climate and spectacular mountain scenery that attracts millions of tourists each year. The population is varied, composed of a mix of Asian immigrants, native Hawaiians, and settlers from the U.S. mainland.

Natural Features

Lying in a line that extends from southeast to northwest, the Hawaiian Islands themselves are the visible portion of a submarine mountain range, built through volcanic activity. The bases of these volcanoes lie some 5,000 m (18,000 ft) below sea level on the deep ocean floor of the mid-Pacific. The islands formed as the Pacific crustal plate moved slowly over a geological hot spot that sent an upwelling of magma, or molten lava, toward the earth’s surface. This process gradually created each of the islands. The older islands, located in the west, are no longer volcanically active. They display various degrees of erosion, which often creates rugged and visually impressive terrain. The big island of Hawaii in the east is the only island that remains volcanically active.

The mountainous terrain, characterized by steep slopes, precipitous cliffs, and rugged canyons, dominates the physical environment of Hawaii. The two highest volcanic peaks in the region, both found on the big island of Hawaii, are Mauna Kea (elevation 4,205 m/13,796 ft), and Mauna Loa (elevation 4,170 m/13,680 ft). Mauna Loa is the world’s largest active volcano, estimated to have collectively discharged more lava than any other volcano in history. Lava and ash have covered thousands of acres of land, displaced entire communities, and disrupted transportation on the islands. During eruptions, lava often pours into the ocean, generating steam clouds and super heating coastal waters.


Tourism has become the most lucrative and fastest growing sector of the Hawaiian economy as 6.5 million visitors find their way to the region each year. Tourists crossing the Pacific from either direction stop to take advantage of the mild climate, the extraordinary scenery, and the ocean beaches. Defense expenditures generate the second highest amount of wealth in the area, with the federal government employing almost 20 percent of Hawaii’s labor force. Hawaii is the headquarters of the U.S. Navy’s Pacific Command because of its strategic location in the middle of the Pacific Ocean. Hawaii has 449,201 hectares (1,110,000 acres) of farmland, devoted to sugarcane, pineapples, and tropical specialty crops, such as coffee. However, most of Hawaii’s agricultural land is used for cattle ranching.


In 2008 Hawaii’s population was 1,288,198 and was very diverse, with no single ethnic group forming a majority. The original island inhabitants are thought to be Polynesian, or Pacific Islanders, who may have arrived as early as AD 750. Beginning in the mid-1800s, immigrants from China, Japan, the Philippines, Korea, Samoa, and other Pacific islands moved to Hawaii in response to U.S. sugar planters’ need for inexpensive labor. According to the 2000 census, people of Asian ancestry make up 41.6 percent of Hawaii’s permanent population. In recent years, a large influx of whites has added to the rich and complex “melting pot” found in the Hawaiian region. During the 1980s, Hawaii’s population grew by 23 percent, with the majority of this growth occurring in the city of Honolulu, located on the central island of Oahu.

Honolulu is the major city of the islands and the state capital. Approximately 75 percent of Hawaii’s citizens live in this metropolitan area, making it the state’s dominant economic, political, and population center. The islands’ other main urban centers, also located on Oahu, include Aiea, Kailua, Kaneohe, Pearl City, and Waipahu. All have fewer than 50,000 residents.


Many people confuse weather with climate. Although the two are closely related, they have distinctly different meanings. Weather changes from day to day and sometimes from one hour to the next. It involves the temperature, precipitation, humidity, and wind factors at a particular time. Short-term decisions about matters such as whether to play baseball during the afternoon or carry an umbrella to work are based on weather.

Climate, however, represents weather conditions over extended periods of time. Repeating cycles of precipitation and temperature, along with complex interactions of wind patterns and seasonal sun, give us our climates. Long-term decisions about storing heating fuels, planning for irrigation, raising particular crops, or choosing particular features for housing designs all require a consideration of climate. The United States is a large country, and different types of climates are found in different parts of the country.

Climate and Soil

Climate has a profound effect on soil composition. Soil types are composed of minerals, organic matter (decaying plant and animal material), water, and air. Soils differ depending on how much of these different ingredients they contain, and climate contributes to those differences. Climatic conditions, such as high wind and heavy rain, can accelerate the breakup of rocks into the small particles that form the basic material of soil. In addition, precipitation controls the movement of nutrients and chemicals in soils. For example, continuous heavy rains can cause leaching, a percolating process that carries away minerals that support plant life.

Climate also affects soils indirectly by acting through vegetation and animal life. A favorable climate that supports a large number of plants and animals may produce more productive soil due to the presence of humus, decaying plant and animal material that adds rich nutrients to the soil.

In the United States, soil characteristics vary considerably by climatic region. For example, soils in cooler continental climates are known as podzols, a soil type that is not very fertile. The leaching action of heavy rain and water runoff removes many of the nutrients from podzols. Lateritic soils, one of the least fertile soil types, are found in wetter and hotter climates. They are the dominant soil type in the southeast, particularly in Georgia, Alabama, and Mississippi. Rich, dark soils called chernozems are found in the Midwest and in grassland areas to the west. These are some of the richest soils in the world.

Climate and Ecological Systems

Climate plays a crucial role in establishing a region’s ecological system. Climate influences the processes that make soil, and it interacts with the soil to determine what plants and animals are able to live in a particular place. A dry, hot climate with poor soil will limit the variety of plants and animals to those specially adapted to survive on small amounts of water and few nutrients. On the other hand, a wet and warm climate with productive soil will promote a rich and varied range of plant and animal species.

Climate also influences the living habits of humans. Individuals in regions with severe winters wear heavy clothing to protect themselves from the cold, and they live in houses that are insulated for warmth. Those who reside in tropical regions wear lighter clothing and live in houses with maximum ventilation for relief from the heat. Economically, climate has a strong effect on agricultural activities. In climates that have long warm seasons and plentiful rain, agricultural crops thrive, but in drier regions, cattle ranching tends to be more prominent.

In order to understand all of the complexities of climates, geographers have long classified them according to temperature, moisture, and vegetation. As a result, unique plant varieties came to be associated with certain climatic regions. Also, animal groups depend on particular kinds of vegetation for food. When a natural interactive system of plants and animals develops, it is called an ecosystem. It includes the living organisms–plants, animals, bacteria, and viruses–as well as the nourishing matter they depend on. Nonliving matter includes water, soil nutrients, oxygen, and carbon dioxide from the air.

Ecosystems consist of all the plants and animals in a specific area and the ways in which they interact with nonliving elements of the environment. Ecosystems exist in water (both fresh and salt water) and on land, and they also include interactions with atmospheric influences. Examples of natural ecosystems are the equatorial and tropical zone rain forests, the monsoon forests, subtropical evergreen forests, midlatitude deciduous forests, cold needle-leaf forests, tall grass prairie, semideserts, desert, and arctic and alpine tundra.

Climatic Regions of the United States

Because of its midlatitude location and vast size, the United States experiences a wide variety of climates. At one extreme are the tropical islands of Hawaii; at the other, the arctic conditions of northern Alaska. The majority of Americans live between these two extremes in a group of climatic regions with unique moisture and temperature patterns.

Geographers have traditionally divided the 48 contiguous United States into two broad patterns of continental climate: the humid East and the arid West. The dividing line most often used is 100 degrees west longitude, an imaginary north-south line extending through the Great Plains from Texas to North Dakota.

The humid east receives abundant precipitation throughout the year. Winters in the northern part are very cold with much snowfall. In the southern part, rainfall is plentiful; summers are very hot but winters are mild. Because of its bountiful moisture, the humid east has also traditionally been a very important agricultural area. Once a land of vast forests, early settlers cleared the land as they moved westward. In some areas, cleared lands were cultivated, abused, exhausted, and eroded away. In other areas, vast forests have been replanted, as in the South, the Appalachians, and parts of the Midwest.

A climatic transition zone occurs on either side of the 100 degrees west longitude line. The eastern woodlands gradually give way to tall grass prairies, which in turn give way to steppes, where short grasses flourish. Few natural tall grass prairies exist today on the Plains. Over the past few centuries, farmers cultivated and planted most of the region with corn or wheat.

In the arid West, precipitation diminishes from east to west and eventually reaches the point where it becomes impossible to raise crops without irrigation. Some desert areas of Arizona, Nevada, and southern California receive less than 125 mm (5 in) of precipitation annually. The grazing of livestock is an important agricultural activity in these areas of mesquite bushes and cacti.

Not all of the West is dry. In fact, one of the wettest areas of the United States is located in the Pacific Northwest. On the west-facing slopes of the Cascades and the Coast Ranges, moisture-laden winds blow from the Pacific Ocean and drop their rain on the mountain slopes. This type of mountain-induced rainfall is known as orographic precipitation. It occurs when wet air rises along the slope of a mountain. As the air moves upward into cooler temperature zones, it expands and cools, releasing the moisture as precipitation. Because of this effect, the climate of the Northwest is cool and moist, and the land is covered with vast, coniferous forests.

Humid Continental Climates

The eastern part of the United States includes two climate types: Humid Continental and Subtropical. Humid Continental is the largest climate type in the United States. It has two subtypes: those areas with hot summers and those with warm summers. The Humid Continental climates are transitional climates between the severe Subarctic climate region in Canada and the warmer Humid Subtropical region of the southern and southeastern United States. These climates are battlegrounds between cold polar air masses surging southward and tropical air moving northward. Humid Continental climates have four distinct seasons and large variations in temperature. They are warm in summer and cold enough to sustain winter snow for some months.

These climate zones were similar to the climates of Europe and allowed European settlers to continue farming as they had in their homelands. They established family farms and concentrated on raising crops and using some of the produce to feed the farm’s livestock. Eventually, this system of general crop and livestock farming spread westward across the United States.

Humid Continental (Hot Summer)

This subregion extends from the East Coast deep into the continental interior, south of the Great Lakes. Located between 35 and 45 degrees north latitude, it includes Rhode Island, Connecticut, Massachusetts, and southern New York, as well as New Jersey, Delaware, Maryland, Pennsylvania, Ohio, Indiana, Illinois, southern Wisconsin, and southern Michigan. Portions of neighboring states are also included.

In this climate zone, winters are cold and summers are hot. January temperatures usually average below 0° C (32° F), while July temperatures average between 18° C (65° F) and 24° C (75° F). Summers are humid with thunderstorms that may produce hail or tornadoes. Annual precipitation averages from 500 to 1,000 mm (between 20 and 40 in). Long, hot summer days provide ideal conditions for rapid plant growth.

Most of the region’s soils are alfisols and mollisols, soil types with a high clay content that retains nutrients. Nowhere else on the continent is there such a large area that combines fertile soils with a humid climate.

The ecosystem generated by this climate supports hardwood forests and grasses. Hardwood forests consist primarily of trees possessing broad leaves, including species such as oaks, elms, hickories, sugar maples, aspens, poplars, and cottonwoods. As settlers established farms, the tall, stiff-stemmed wild grasses that originally grew in this climatic region gave way to cultivated crops.

The famous Corn Belt of the Midwest lies within this climatic region. Corn, soybeans, alfalfa, and hay are significant crops. In the Middle Atlantic area, vegetable gardening is found on the sandy soils of the New Jersey and Delaware coastal plain.

Humid Continental (Warm Summer)

The ‘warm summer’ subregion lies farther north than the ‘hot summer’ area. It falls roughly from 45 degrees to 60 degrees north latitude. It lies astride the United States-Canadian border and includes most of the Great Lakes region. States in this climate zone are Maine, New Hampshire, Vermont, upper New York, upper Michigan, northern Wisconsin, and Minnesota, as well as North Dakota, part of South Dakota, Montana, and sections of surrounding states.

Winters in this area are harsh; snow remains on the ground for periods of up to five months. January average temperatures are less than -15° C (5° F). Summers, on the other hand, are pleasantly cool but short, with average monthly temperatures ranging from 18° C to 20° C (64° F to 68° F). This region is famous for its large annual temperature range. The difference between a warm summer day and a cold winter night may be as much as 40° C (100° F). For much of the region, the frost-free period is less than 150 days per year. The cool, short summers are not especially conducive to farming.

Precipitation is ample in all months; annual precipitation averages 800 mm (32 in). In the summer, precipitation is high when thunderstorms form along moving cold fronts and squall lines. Much of the winter precipitation is snow, which remains on the ground for long periods. The western area of prairie is a bit drier than the east.

The soils vary in the region, but spodosols are dominant. They are naturally poor soils in terms of agricultural productivity. Fertile mollisol soils are found in the Great Plains in the western part of the region. These soils support grasslands.

Much of this region was originally covered with a mixture of woodland and forest. The vegetation in the area has changed since the arrival of European settlers, who introduced nonnative trees and plants to the region. In the 20th century, dominant tree species included pitch pine, oak, hickory, and maple.

Around the Great Lakes, dairy farming became important because dairy cattle can graze on the rich grass that grows in this moist climate. The Great Lakes region is the dairy center of the United States and is well known for the production of cheese and butter. Potatoes and other root crops, along with hay and some hardy grains, are the primary agricultural crops.

Humid Subtropical

This climate region, characterized by long, hot, sultry summers, is found in the southeastern United States. North Carolina, South Carolina, Georgia, Alabama, Mississippi, Louisiana, Florida, and portions of surrounding states are included. In some areas, the growing season lasts for eight months or more.

Temperatures average 26° C (80° F) in the summer and range from 4° C to 10° C (40° F to 50° F) in the winter. The Humid Subtropical climate receives ample precipitation, averaging about 760 mm (30 in) annually in the western part of the region to more than 1,500 mm (60 in) per year in the southern part. Most precipitation occurs in the summer months as rainfall. A polar air mass can push southward and bring an infrequent snowstorm, but snow seldom stays on the ground for more than a few days.

Ultisols are the dominant soil type of this climatic region. This red soil is less fertile because abundant summer rainfall leaches mineral nutrients from the topsoil. Without fertilizers, these soils can support crops for only two or three years before nutrients are exhausted. The use of fertilizer extends land use in this climatic region.

The natural vegetation in the Humid Subtropical climate zone is the subtropical evergreen forest. This forest occurs in two forms: broadleaf and needle-leaf. The subtropical broadleaf evergreen forest often has a well-developed lower layer of vegetation, including ferns, small palms, shrubs, and herbaceous plants. The subtropical needle-leaf evergreen forest of the southeastern United States is known as the southern pine forest. Loblolly and slash pines dominate the uplands. Bald cypress grows in the swamps of this area. Timber companies have created many plantations in the area yielding valuable lumber and pulp.

The long growing season, ample precipitation, and the substantial use of fertilizers and other additives necessary for high, sustained crop yields makes this region an important agricultural area. Rapid tree growth supports the pulp, plywood, and lumbering industries. Specialty crops such as tobacco, cotton, sugarcane, citrus fruits, and rice are also grown.


The Semiarid climates are found in sections of the Great Plains regions, parts of Texas, New Mexico, the intermontane basin of Nevada, parts of eastern Washington and Oregon, and sections of neighboring states. This climate is a transitional one between the desert types and the humid types.

The temperature range is extreme. During winter the temperature can drop as low as -1° C (30° F). Summer temperatures often are in the upper 30°s C (lower 100°s F). Average temperatures vary across this large region extending from Canada to Mexico. For example, in eastern Washington state, January temperatures range from less than -7° C (20° F) to -1° C (30° F) and often drop down to -18° C (0° F). July averages are from 18° to 24° C (65° to 75° F). Temperatures are considerably higher in Las Vegas, Nevada, located at the southern end of the region. The average July temperature is 32° C (90° F) and the highest temperature ever recorded there was 48° C (118° F). The average high temperature in Las Vegas in January is in the lower 10°s C (lower 50°s F) and average lows are near freezing. Annual rainfall is from 250 to 500 mm (from 10 to 20 in), which is enough to support grasses but not enough to maintain a forest cover. Rainfall in the semiarid climate is sparse and unpredictable.

The region’s aridisol soil is alkaline and supports very sparse vegetation. With irrigation, it can support crops but not without encountering problems such as salt buildup and waterlogging. Despite these problems, the steppe grasslands are used for some grain cultivation. Hay and alfalfa are common agricultural products.

The steppe has a vegetation type consisting of short grasses occurring in sparse clumps or bunches. Scattered shrubs and low trees may also be found there. The steppe occupies vast regions of semidesert. Cattle, sheep, and angora goats are adaptable to the steppe, where they graze over vast acres of open range. Skunks, raccoons, coyotes, snakes, rodents, and pronghorns also inhabit the ecosystem.

America’s Wheat Belt lies on the Great Plains. In the southern portion (Kansas, Nebraska, and Colorado) farmers sow winter wheat in the fall to be harvested in the spring. In the northern part (North Dakota, South Dakota and parts of Montana), where winters are more severe, farmers sow the seeds in the spring and harvest the crop in the fall.


The most arid climate in the United States is found in the Southwest. This area comprises southern inland California, Arizona, New Mexico, and parts of Nevada and Texas. Sections of neighboring states are also included. Moisture is meager and erratic. The area receives less than 250 mm (10 in) of rainfall annually. High temperatures cause any moisture to evaporate rapidly.

Many areas with arid climates can be found on the dry side of mountain ranges. These mountains create a rain-shadow effect, with a belt of arid climate to the leeward side (the side opposite the prevailing winds) of the mountain barrier. Air that has released its moisture while passing over the mountain summit descends the leeward slopes of the range and is compressed. Cooling no longer occurs, and cloud droplets and ice crystals evaporate. The air continues to warm as it descends. By the time it reaches the base of the mountain, the air is hot and dry because it has released its moisture.

Temperatures are higher in the desert than in any other climatic region because clear desert skies allow the earth’s surface to heat up rapidly during the day. In the evening, temperatures drop quickly, resulting in great variations in temperature within a 24-hour period. Winter is brief and mild. Summer is long and scorchingly hot. Temperatures during the hottest months average from 29° C to 35° C (from 85° F to 95° F), and the midday readings of 40° C to 43° C (105° F to 110° F) are common. The winter daily maximum usually averages 18° C to 24° C (65° F to 75° F). Winter nights are chilly, averaging 7° C to 13° C (45° F to 55° F).

Soils in the desert climate are classified as aridisols. They are low in organic matter and high in salts. Humus is lacking because the climate supports only a very sparse vegetation.

Vegetation has adapted to conditions in the desert. Cacti and other succulent plants store water in their thick leaves. Shrubs especially adapted to the desert, such as sagebrush and creosote bush, have special forms of roots and stems. Their waxy leaves help them limit water loss. Because there is little moisture in the soil, the ground between plants is generally barren in the desert. Some desert plants are small flowering annuals that can remain dormant for long periods and quickly germinate when water becomes available. Following a rare shower, the desert landscape is often painted with brightly colored flowers that bloom for a brief period.

Like the plants, animals that live in deserts have become adapted so that they require less water. Most desert animals have small bodies, which help them more easily dissipate heat. Some burrow into the ground when the hot sun beats down and then come out at night to feed. Small desert animals include mice, hares, rabbits, kangaroo rats, and spade foot toads. Among the larger desert animals are the coyote, and mule deer.

Historically, few people have lived in desert regions. Settlements occurred only where a natural oasis or a permanently flowing stream existed. The desert was extremely marginal land that was used for occasional grazing of cattle, sheep, and goats. However, many deserts have soils rich in the minerals that plants need to grow. When these deserts are irrigated, they grow abundant and useful crops such as vegetables, fruits, and grains.

With the ability to pump groundwater, divert streams, and build dams and reservoirs, the desert Southwest boomed. Large urban settlements, retirement communities, and irrigated agriculture all expanded. However, in many areas, groundwater is being withdrawn from aquifers (underground reserves of water) faster than the aquifers are being recharged. Consequently the future of water supplies in California and the Southwest has become a matter of serious concern for residents and businesses that depend on groundwater.


The Mediterranean climate of central and coastal California is characterized by dry summers and mild, rainy winters. The name was given to this climate because it is also found in areas bordering the Mediterranean Sea.

Summer temperatures range from 20° to 25° C (70° to 80° F), and winter temperatures are a mild 4° to 10° C (40° to 50° F). The average precipitation of 360 mm to 640 mm (14 in to 26 in) per year occurs during the cool winter season and contrasts sharply to the area’s dry summer months. There is a complex variety of soils in this region, which vary greatly in moisture, temperature, slope, and elevation.

The Mediterranean climate pattern reverses the traditional growing seasons: Plants thrive in the wet winter and wither during the dry summer. In order to survive the dry summers, plants have developed deep taproots, thick bark, and leathery leaves to obtain and conserve moisture. These types of plants are called sclerophylls. Trees are relatively small, with branches close to the ground and gnarled trunks. Chaparral, a low-growing woody shrub, dominates the valleys and lower mountain slopes. Sclerophyll forests grow along the California Coast Ranges, where live oak and white oak dominate. Grassland occupies the open ground between the scattered oaks. Game birds include grouse, mourning doves, and quail. Deer, foxes, minks, wildcats, wolverines, and a few mountain sheep roam the mountain and forest areas.

To allow crops to grow during the summer months, large-scale irrigation projects have been constructed. Most irrigation occurs in the Great Valley of California, where the Central Valley Water Project provides water through a series of dams and aqueducts. Irrigation has transformed this area into a region of high productivity; the total value of farm products sold in California is higher than in any other state.

In the 1990s California with its numerous vineyards was the major wine producer in the nation. The climatic conditions and rich alluvial soils in valleys allow California farmers to grow more than 200 different crops, making the state one of the nation’s leading agricultural producers. Dairy cows, livestock, and poultry also flourish.

Marine West Coast

The Marine West Coast climate stretches from northern California through the coastal sections of Oregon, Washington, and southern Alaska. Mild winters and summers distinguish this climate, even though inland climates at the same latitude have bitter winters and hot summers.

In the Marine West Coast region, summer temperature averages range from 15° C to 20° C (from 59° F to 68° F), and the coldest months have a temperature range of 4° C to 10° C (40° F to 50° F). These locations receive the prevailing westerly winds, which bring moist air off the Pacific Ocean. The Marine Northwest experiences frequent storms involving cool, moist air masses. Where the coast is mountainous, the moist air from the ocean rises as it climbs over the mountains and releases its moisture; the result is high annual precipitation with extensive cloud development and profuse rainfall. With the exception of a few warm, sunny summer months, the area experiences fog, drizzle, and gray, leaden skies almost daily. The annual total rainfall may be as much as 1,450 mm (57 in), most of which falls during the winter months.

The region has thin podzol soil, which is poor in agricultural productivity because of excess acidity. Farmers must apply lime and heavy fertilizers to make agriculture viable. Agricultural crops include deciduous fruits (apples and pears), berries, grapes, winter wheat, and horticultural items. Because of the mild winters and lush grasses, dairy farming is also an important agricultural activity.

The Marine West Coast is a land of magnificent coniferous forests with huge stands of tall trees, particularly Douglas fir. In California, some giant sequoias, known as redwoods, reach heights of more than 90 m (300 ft).


The Subarctic climate is found in most of interior Alaska, reaching as far north as the Arctic Circle (60° north latitude), where it gives way to a Tundra climate zone. Summer is very brief in the Subarctic climate and lasts for one to three months. Summer temperatures average about 10° C (50° F). Winter arrives as early as October. During winter some areas experience average temperatures of less than -15° C (5° F) for at least three or four months. Precipitation is usually less than 500 mm (20 in) annually, and most falls as rain during the brief summer. During the winter, when the region is dominated by cold, dry air masses, precipitation is meager. Snow may accumulate to depths of one foot or more.

Because the earth’s axis is tilted, daylight hours vary considerably in the extreme northern latitudes of Alaska. During the summer months, when the North Pole tilts toward the sun, days average 17 to 22 hours of sunlight. During the winter, when the pole tilts away from the sun, nights with 18 hours or more of darkness are the rule.

The soils of the Subarctic climate are inceptisols, which form primarily from minerals that are broken down by frost action and glacial grinding. Inceptisols are young, undeveloped soils that tend to easily lose their mineral content. Layers of peat, a dark brown organic matter composed of partially decayed vegetation, are often present between the mineral layers.

One characteristic of the Subarctic climate is permafrost, permanently frozen subsoil. Summer warmth thaws only the upper 1 to 4 m (3 to 12 ft) of frozen soil. Because surface water cannot drain into the frozen subsoil, swamp and bog conditions develop during the summer months. These wetlands become home to countless mosquitoes and black flies. Permafrost requires that buildings be constructed to prevent heat losses. Escaping heat can melt adjacent frozen subsoils, causing construction projects to slowly sink into saturated soils.

Although the ground is waterlogged during the summer, the soil is frozen much of the year, and water is accessible to plant roots only during the short warm season. Many of the region’s trees are xerophytic in nature, meaning that they have adapted to dry weather conditions by developing special features that allow them to retain water. The Subarctic contains a vast needle-leaf type of forest known as taiga. The forest consists of relatively few tree species, including the jack pine, balsam fir, white and black spruce, poplar, and willow trees. On the shaded forest floor, vegetation is meager; mosses and lichens are the most common plant forms.

Animal life is not as abundant as in the midlatitude forests further south. Caribou, wolf, bear, fox, otter, mink, ermine, squirrel, lynx, and sable inhabit the Subarctic. Trapping is an important occupation, as animals living in the cold climate tend to grow heavy fur pelts.

This area is not highly favorable for human settlement because the growing season is short and the impoverished soils of the region limit agricultural opportunities. A few crops, such as potatoes and hardy grain, are raised in this climate. The sparse population of the area supports itself by logging, fishing, and mining, and by trapping animals.


Tundra climate extends north of the Arctic Circle, from the Subarctic region to the Arctic Ocean. Like the Subarctic region, the Tundra experiences extremely long periods of daylight in the summer and extended periods of darkness during winter months.

Here, only two to six months of the “warm” season are above freezing, and frost may occur on any day of the year. The average temperature for July, the warmest month, never exceeds 10° C (50° F). Temperatures vary according to location, but data recorded at the weather station at Barrow, Alaska, the northernmost community in the United States, show average temperatures of –25° C (–13° F) for January and 4°C° (39° F) for July.

Annual precipitation is less than 360 mm (less than 14 in), and much of the precipitation falls during the warm season in the form of rain or occasional wet snows. The meager winter snowfall is usually dry and powdery so that it forms a very compact cover. Frequently, the small amount of snow that falls is blown by strong winds. Since no forests break the force of the wind or anchor the snow cover, the wind blows the snow into drifts while leaving patches of bare ground.

Tundra soils are largely undeveloped inceptisols. More specifically Tundra soil is of the subdivision cryaquepts, meaning “icy cold,” because permafrost appears close to the surface at a depth of about 40 to 60 cm (16 to 24 in). When not frozen, the top layer of soil is permanently saturated with water, and the prevailing soil conditions are those of a bog. Unlike bogs found in the midlatitudes, the Arctic region’s large areas cannot be drained and are unsuited to agriculture. Better-drained sites of the Arctic fringe regions have soils that are slightly richer in organic material.

There are no trees; natural vegetation consists of mosses, lichens, short bushes, and sedges. These plants provide food for grazing caribou, musk ox, and reindeer. Seals, walruses, and whales are found in adjacent seas. Polar bears roam the shore and nearby ice floes to search for seals and other marine creatures.

Tropical Rain Forest

Hawaii, a chain of islands more than 3,000 km (2,000 mi) from the mainland, is the only U.S. state outside North America and the only one with a Tropical Rain Forest climate. Hawaii’s rain forests thrive in wet windward locations (essentially the northeast sides of the islands). Steady trade winds blowing from the northeast push moist ocean air over the land. As moisture-laden winds rise over the island’s volcanic mountains, the air expands, cools, and becomes incapable of retaining moisture. Heavy rains result.

As the same air descends on the leeward side of a mountain (the side away from the wind), it contracts, becomes warmer, and absorbs more moisture; thus rainfall is unlikely. For example, Mount Waialeale, on the island of Kauai, is the wettest place on earth, with an average of 11,455 mm (451 in) of rain annually. Yet the city of Honolulu, located on the dry southern coast of Oahu, faces water shortages with a 640-mm (25-in) average annual rainfall.

Although the islands lie within the hot climate zone of the tropics, the continuous Northeast trade winds produce pleasant sea breezes that moderate the temperature. July temperatures average around 21° C (70° F), and winter temperatures are only slightly lower.

The average soil in agricultural areas is red (due to high iron content), moderately fertile, and relatively productive for agriculture. Most of the soils are highly weathered, and water has leached much of the humus from the soil. The better-watered areas are noted for thick growth of tropical trees and shrubs. In dry areas, the dominant vegetation includes xerophytic plants, which have special characteristics to retain moisture.

The Hawaiian Island chain is one of the most remote groups of islands in the world, isolated from the world’s continents by the vast expanses of the Pacific Ocean. This isolation engendered a variety of native plants and animals. Although the islands have a limited variety of species, these exhibit many unusual characteristics. Nearly 15 bird species and all native varieties of plants are unique to the islands. Only one species of mammal, the hoary bat, is native to the island. Because of human carelessness, numerous species of animals and plants are either rare or endangered. Both the hoary bat and monk seal are endangered, as well as 227 species of plants and 250 insects.

Warm temperatures, abundant precipitation, and moderately fertile volcanic soils encourage the growth of tropical fruits and vegetables. Pineapples and sugar cane were the leading crops for a century, but agriculture at the end of the 20th century was more diverse. Specialty crops include papayas, macadamia nuts, and exotic flowers. Because of its tropical climate, Hawaii is the only place in the nation that raises coffee.


Water features, including lakes, rivers, and coastlines, have played an important role in the development of the United States. For centuries, Native Americans used rivers, lakes, and coastal waters extensively for transportation and as a source of food and drinking water. Beginning in the 16th century, the first Europeans arrived by sea in what would become the United States, settling along coastal regions and exploring inland on water routes such as the Mississippi and St. Lawrence rivers and the Great Lakes. In the 17th and 18th centuries, English colonists in settlements along the Atlantic coast relied on sea trade with Europe, both as an origin of essential imports and a destination for exported goods.

Before railroads were extended across the western frontier, settlers traveled by river as they moved away from coastal settlements into the interior of the continent. The Ohio River was the main water route leading to the old Northwest Territory west of the Appalachian Mountains. When the United States purchased the Louisiana Territory from the French in 1803, the Mississippi and Missouri rivers provided access to the newly acquired lands of the west.

Water transportation remains important to the American economy today. Shipping commodities by water is time-consuming but relatively inexpensive, especially for commodities that are bulky, but relatively inexpensive by weight, such as coal, wood products, petroleum, metallic ores, and foodstuffs. Oceans, rivers, lakes, and canals are used to carry enormous quantities of raw materials and finished products throughout the United States as well as to overseas destinations. The coastlines of the United States are dotted with port cities that serve as gateways for goods being exported from or imported into the country.

The fresh water provided by U.S. lakes and rivers also plays an important role as a natural resource. Vast quantities of water must be available for basic daily activities, including drinking, cleaning, and washing, as well as for commercial activities, such as crop irrigation and industrial production. Arid regions of the nation, such as the desert Southwest and southern California, as well as many large U.S. cities, including New York and Los Angeles, have outgrown local supplies. Water must be piped to these locations from sources hundreds of miles away.

Americans have addressed water distribution problems by building dams, reservoirs, and other engineering projects. The structures found in the eastern portion of the United States, such as the dams constructed in the Appalachian region, were built largely for flood control. Many of those located in the West were built primarily to irrigate arid land; one example is the Central Valley Project in California. See also Water Policy in the American West.

These water control programs have important secondary uses, such as generating electricity and creating recreational opportunities. Hydroelectric facilities, particularly in the Pacific Northwest and in the Tennessee Valley, provide considerable electrical energy. The reservoirs behind many of the country’s larger dams afford a variety of recreational water activities that otherwise would not be available.

Major Lakes and River Systems

Two enormous drainage systems dominate the U.S. landscape: the Great Lakes-St. Lawrence River and the Mississippi-Missouri rivers drainage areas. More than 75 percent of the freight moved along U.S. inland waterways moves on these waterways.

The Great Lakes-St. Lawrence River system serves the northern reaches of the country, from the Midwest to the eastern seaboard. The St. Lawrence Seaway, an extensive network of waterways and locks, allows ship traffic to pass between the Great Lakes and the Atlantic Ocean.

The Mississippi-Missouri River drainage system encompasses much of the central United States. The headwaters of the Mississippi are located in Lake Itasca in Minnesota, and the Missouri originates in the Rocky Mountain region of Montana. This huge system also includes the Ohio River, draining the Midwest and the northern segment of the Appalachian Mountains, and the Tennessee River, dominating the southern Appalachian region.

Several other river systems have played important roles in the economic and cultural growth of the United States. In the Pacific Northwest, the Columbia River and its tributaries drain much of the northern Pacific coastal mountain ranges. The semiarid and arid lands of the Southwest get life-sustaining water from the Río Grande and Colorado river systems. The Central Valley of California depends on irrigation networks linked to the Sacramento and San Joaquin rivers. The rugged interior regions of Alaska have become accessible largely because of river transportation on the Yukon River and its tributaries.

Major Lakes

Great Lakes

The Great Lakes, forming the largest continuous freshwater body in the world, include five massive inland lakes (Superior, Huron, Michigan, Ontario, and Erie), encompassing 244,100 sq km (94,250 sq mi) in the upper reaches of the midwestern United States. Lake Michigan is the only one of the lakes that is located entirely in the United States. The other four lakes lie on the border between the United States and Canada.

Several thousand years ago, these enormous water features were shaped when an ice sheet extended over the region and created five large depressions. As the ice sheet receded, meltwater filled the basins and created the lakes. While many streams and rivers flow into the Great Lakes, the St. Lawrence, beset with rapids and waterfalls, offers the only natural outlet to the Atlantic Ocean.

During the early part of the 19th century, the Great Lakes were of only limited value as a transportation route because rapids and waterfalls prevented ships from traveling across the Great Lakes and down the St. Lawrence to the Atlantic Ocean.

Transportation improved when a number of canals were built between the various lakes and between the lakes and the Atlantic Ocean. The Erie Canal, connecting Lake Erie with New York’s Hudson River, opened in 1825. The canal offered the first navigable water connection to the East Coast from the lakes region. Small ships and barges began to move raw materials and supplies to and from the Great Lakes area. The Welland Ship Canal, built in 1829 to bypass Niagara Falls, made the Great Lakes accessible to small oceangoing vessels via the St. Lawrence River. In 1855 the Sault Sainte Marie Canal opened, enabling lake traffic to proceed from Lake Superior to Lake Huron. As settlers began to flow into the Great Lakes territory, inland port cities and other urban settlements grew.

In the late 1950s, the U.S. and Canadian governments cooperated to build the St. Lawrence Seaway to allow large oceangoing vessels access to the Great Lakes. The seaway consists of 720 km (450 mi) of improvements to the St. Lawrence River, which flows mainly through Canada. These improvements included numerous locks and canals between Lake Erie and Montréal, Canada. The Seaway’s 8.2-meter-deep (27-foot-deep) channel is not adequate to handle today’s largest oceangoing vessels and containerships.

The Great Lakes-St. Lawrence system is a waterway of major commercial importance, even though it is open for navigation only nine months of the year. In the winter, ice blocks the channels and the edges of the lakes. This waterway is used to ship bulk cargo, including iron ore, grain, limestone, timber, and coal, among inland ports of the region, the Atlantic coast, and beyond. It has allowed many Great Lakes port cities to become international trade centers.

Today, almost 20 percent of the U.S. population lives along the shores of the Great Lakes, concentrated in five large cities: Chicago, Illinois; Milwaukee, Wisconsin; Detroit, Michigan; Cleveland, Ohio; and Buffalo, New York. These urban centers benefit greatly because of the movement and manufacture of goods throughout the Great Lakes region.

Great Salt Lake

The Great Salt Lake is located in Utah and lies within the Great Basin, an inland water drainage area that encompasses most of Nevada and parts of Utah, Oregon, Idaho, and California. The Great Salt Lake is the remnant of Lake Bonneville, the largest of many lakes formed in the region when retreating ice sheets melted at the end of the last Ice Age. The Great Salt Lake acquired its name because its water has a high salt content. The lake receives mountain runoff that carries suspended salts, and it has no outlet to the ocean because high mountains surround the Great Basin. The streams and rivers that replenish the Great Salt Lake flow only intermittently. The Great Salt Lake varies substantially in size, depending on precipitation, the amount of runoff that replenishes the lake, and the amount of water that is pumped out for irrigation.

As the frontier of the United States expanded westward in the 19th century, many people traveled through the Great Basin on the way to the West Coast. Few decided to settle there permanently. One notable exception was the Mormon pioneers, members of a religious group who began arriving in the area as early as the 1850s. In their search for religious freedom, they settled near the shores of the Great Salt Lake, began raising crops with irrigated farming, and built a settlement that became Salt Lake City, the region’s major urban center.

Major Rivers

Mississippi River

As North America’s longest river, the Mississippi River flows 3,770 km (2,340 mi) from its source at Lake Itasca, Minnesota, to its mouth at the Gulf of Mexico. In addition to the Great Lakes system, the Mississippi drainage complex is one of the two largest natural inland waterway systems on the continent. The Mississippi River and its network of tributaries, which includes the Ohio, Missouri, Tennessee, Arkansas, Red, and Illinois rivers, drains most of the central United States. In some areas, the main channel of the Mississippi reaches a width of nearly 1.6 km (1 mi). The river has a channel ranging in depth from more than 7 m (more than 25 ft) in New Orleans, Louisiana, to 2.7 m (9 ft) in Saint Paul, Minnesota. Deepwater vessels can navigate the river as far north as Baton Rouge, Louisiana, while smaller ships can navigate the Mississippi for more than 2,900 km (1,800 mi).

As early settlers moved away from the Atlantic coast, they used the Mississippi River system to travel to interior locations and to ship their agricultural products to markets. New Orleans, situated on the Mississippi about 160 km (about 100 mi) north of the Gulf of Mexico, became an important shipping and trade center. At first people and goods traveled on flatboats, which were powered by oars or poles. Then in the early 1800s, engine-driven steamboats were introduced, offering improved transportation and shorter travel times. Steamboats led to increased trade and travel on the Mississippi, and several urban settlements, including St. Louis, Missouri, quickly grew to become major inland ports.

The Mississippi still serves as an important transportation route to and from America’s Heartland, especially for barges loaded with raw materials, crops, and other bulky goods. More than half of the freight transported on inland waterways in the United States travels on the Mississippi. Dams built for flood control and power generation lie along the entire course of the waterway, and locks provide a means for vessels to bypass these structures.

Several large manufacturing, service, and transportation centers have developed along the Mississippi River system because of the traffic along the waterway. These include Saint Louis, Missouri; Saint Paul, Minnesota; and Memphis, Tennessee. New Orleans, Louisiana, has become the busiest port city in the Southeast.

Ohio River

The Ohio River is one of the main tributaries of the Mississippi River, draining the northern portions of the Appalachian Mountains and the Midwest. At a length of 1,580 km (981 mi), the Ohio River is relatively short compared with other major rivers in the United States, yet it played a major role in the opening of the American Midwest to settlement. It became the main transportation route leading westward from the eastern portion of the United States, and until the opening of the Erie Canal, it was the safest, cheapest, and most convenient way to ship freight to and from the interior regions of the continent.

As settlers moved westward along the Ohio River, urban centers began to develop along these routes. These centers included cities such as Pittsburgh, Pennsylvania; Cincinnati, Ohio; and Louisville, Kentucky. The river provided the means for moving the Appalachian coal that fueled Pittsburgh’s steel industry, as well as for transporting the finished steel to market. More than 800 km (500 mi) of the Middle Ohio Valley developed as a major heavy-manufacturing district, centered on the inexpensive transportation offered by the river.

Originally, the Ohio River was too shallow in many places for transportation during the dry months of late summer. To correct this, the federal government built a network of more than 40 dams along the river’s course, creating a waterway deep enough to sustain reliable navigation. As a source of inexpensive and dependable transportation, the Ohio has become one of America’s leading carriers of bulk commodities, such as coal, iron ore, sand, steel, and gravel.

Tennessee River

The 1,050-km (652-mi) Tennessee River drains much of the southern Appalachian Mountains before it joins the Ohio River in western Kentucky. Improvements have made the Tennessee River navigable to small boats as far upstream as Knoxville, Tennessee. In 1985 the Tennessee-Tombigbee Waterway was completed, providing a barge route to the Gulf of Mexico via the Tombigbee River in Alabama. At a cost of $1.8 billion, this was the nation’s largest navigation improvement scheme. Unfortunately, it has failed to increase traffic significantly on the water route.

While almost every major U.S. river has been used for hydroelectric power generation, irrigation projects, or flood control measures, the management of the Tennessee River is the best example of a regional approach to watershed development. The federal government created the Tennessee Valley Authority (TVA) in 1933 partly in response to the desperate economic situation created by the Great Depression of the 1930s.

The TVA built more than 20 dams on the Tennessee River and has improved navigation as far upstream as Knoxville, Tennessee. As a result, the Tennessee Valley became one of the most important hydro-electricity producing areas of the United States. This inexpensive power attracted industries to the region, which has developed as a diversified manufacturing center. As a result, cities such as Knoxville and Chattanooga in Tennessee and Huntsville in Alabama have grown. Due to improved flood controls and extensive conservation measures, agricultural output has improved in the Tennessee River Valley, especially in the Great Valley of East Tennessee.

Missouri River

The 3,726-km (2,315-mi) Missouri River, which originates in the mountains of northern Montana, is a major tributary of the Mississippi. Its drainage basin encompasses most of the northern Great Plains region. Along with the Mississippi and Ohio rivers, the Missouri served as a major water highway, carrying settlers into the interior regions as the frontier expanded westward. However, larger vessels could not use the Missouri because of shifting currents and sandbars.

In 1944 the U.S. government established the Pick-Sloan Plan to improve the Missouri River. The plan addressed the different needs of the two parts of the drainage basin. The western reaches of the river basin receive very little rainfall, less than 380 mm (less than 15 in) per year. In contrast, the eastern end receives more than 1,000 mm (more than 40 in) of rainfall annually. Residents of the western area wanted irrigation systems and reservoirs for storing water. People living in the eastern part of the river valley were interested in hydroelectric power, flood control measures, and improvement of navigation.

The Pick-Sloan Plan called for regional land management, the construction of reservoirs and irrigation projects, improvement of river navigation, and flood control infrastructure along the Missouri River valley. However, the government never implemented a comprehensive plan for the Missouri River valley. Instead it gradually completed individual projects, including the construction of six dams to provide irrigation water, and to regulate water levels in the navigation channel.

During the 1950s and 1960s, as part of the Pick-Sloan Plan, the channel of the Missouri was improved to accommodate high volumes of modern river traffic. Despite a tremendous investment in dams, reservoirs, and other engineering projects, commercial traffic on the Missouri has remained light.

Río Grande River

The Rio Grande River flows southward from its source in the Rocky Mountains for 3,100 km (1,900 mi) until it joins the Gulf of Mexico. Along its entire course from the dry, high plateau region to the humid, flat coastal plain, people have historically depended on water from the Río Grande for drinking, irrigation, and industrial uses.

The demand for this river’s water is so high along its entire route that downstream locations are often left with inadequate supplies for the amount of agricultural acreage under cultivation. There have been occasions when the riverbed of the Río Grande near El Paso, Texas was totally dry. To ensure that Mexico is guaranteed use of a certain amount of the river’s water, the United States agreed to build a series of dams across the Río Grande. Accompanying reservoirs were then used to hold water for use by Mexican citizens.

An increase in international trade between the United States and Mexico has spawned the rapid growth of cities and industries on both sides of the Río Grande. Several trade and transportation centers have developed along the river, including Albuquerque, New Mexico, and El Paso, Texas. Brownsville, Texas, located at the mouth of the river, maintains an excellent deep-water port.

Colorado River

Originating in the Rocky Mountains of Colorado, the Colorado River extends for 2,330 km (1,450 mi) to the Gulf of California in Mexico. The river flows through the extensive, high Colorado Plateau region in the states of Colorado, Utah, and Arizona. For millions of years, the Colorado River and its tributaries have been carving deep canyons, including the scenic Grand Canyon, into the arid Southwestern landscape. Portions of this spectacular feature reach a width of 29 km (18 mi) and a depth of more than 1,500 m (more than 5,000 ft).

As the only major river flowing through the driest portion of the United States, the water of the Colorado is in great demand by several states as well as by Mexico. To meet this demand for water, dams were constructed in the Colorado River drainage basin beginning in the early 1900s. These dams supported large-scale irrigation projects. As the demand for water in the region increased, more dams were constructed to help control water usage and provide electricity to nearby states.

In 1923 the states of the upper basin (Colorado, New Mexico, Utah, and Wyoming) and those of the lower basin (Arizona, Nevada, and California) met to divide usage of the river’s water. The upper basin states agreed upon a subdivision of their total allotment, but the lower basin states went to court to set their distribution shares. Those totals have not been revised for three decades while the populations in many of the areas served by these allotments have grown rapidly. See Water Policy in the American West.

In the 1930s Hoover Dam was built on the border between the states of Arizona and Nevada. It is the largest of four dams built on the lower course of the river and holds back the waters of Lake Mead, one of the world’s largest reservoirs. Beginning in 1973, the Central Arizona Project used a variety of canals, tunnels, pumping stations, and pipelines to carry water from the Colorado to desert cities such as Phoenix and Tucson in Arizona. The Colorado River is the chief source of water for the state of Arizona. Today, there is more Colorado River water claimed through various agreements than actually exists.

Rivers of California’s Central Valley

Mountain ranges surround the Central Valley of California, which is about 640 km (about 400 mi) in length and about 80 km (about 50 mi) wide. To the west are the Coast Ranges, consisting of small mountains of 600 to 1,200 m (2,000 to 4,000 ft). To the east, the massive peaks of the Sierra Nevada Mountains reach a height of 4,418 m (14,494 ft) at Mount Whitney. Two large river systems drain the valley: the Sacramento River flowing southward from the northern end of the valley, and the San Joaquin River flowing northward from the southern portion. These rivers converge and flow into the Pacific Ocean through San Francisco Bay at a break in the coastal mountain barrier.

The northern part of the Central Valley has adequate rainfall for crop cultivation. Substantial runoff from the Sierra Nevada range replenishes the Sacramento River system. However, at the southern end of the valley, the climate becomes drier. Desert conditions exist in much of the southern Central Valley.

Early settlers to the southern part of the Central Valley region recognized the agricultural value of the land and began practicing irrigation agriculture as early as the late 19th century. The Central Valley Project was built in the 1930s to divert surplus water from the Sacramento River to the San Joaquin River in the drier southern region. It was the first part of a system of dams, canals, and pumping stations that draws off water to irrigate about 2 million hectares (about 5 million acres).

By the 1950s, growing urban areas and expanding farmlands were demanding more water than could be supplied by the existing distribution system. The 1960 California State Water Plan provided additional infrastructure to carry more water to address the shortages. In the 1990s, the Central Valley was California’s largest irrigated district and one of the state’s leading agricultural areas, producing about 75 percent of California’s agricultural output. Urban centers such as Sacramento, Fresno, and Stockton serve as distribution centers for agricultural products.

Columbia River

The Columbia River, the principal river of the Pacific Northwest, originates in Canada and flows for 2,000 km (1,240 mi). It occupies a portion of the Rocky Mountain Trench, a huge depression that extends from Montana to the Yukon Territory in Alaska. Its main tributary, the Snake River, drains part of Idaho, Montana, Wyoming, Utah, and Nevada. The Snake joins the Columbia for the river’s lower 480 km (300 mi). The deep valley of the Columbia River forms part of the border between Washington and Oregon, before breaking the north-south trend of the Cascade Mountains and entering the Pacific Ocean.

The river has a steep gradient, descending almost 400 meters (almost 1,300 feet) over its 1,190-km (740-mi) U.S. segment. In addition, it has an annual flow rate of about 8,000 cubic meters per second (about 265,000 cubic feet per second), which is exceeded only by that of the Mississippi and St. Lawrence rivers. As a result, the Columbia possesses the greatest hydroelectric potential of any waterway in North America. A total of 11 dams have been constructed on the river in the states of Washington and Oregon to improve navigation and produce electricity.

The Rock Island Dam built in Washington in 1929 was the first dam built on the river. In the 1930s the Grand Coulee Dam, also in Washington, was completed. As the largest hydroelectric plant in the world, and one of the largest dams in the nation, it impounds water used to irrigate more than 400,000 hectares (more than 1 million acres) of semiarid land in central Washington. Many other dams have been constructed on the tributaries of the Columbia River. Large urban areas in Washington and Oregon use most of the power produced in the Columbia Basin.

Spokane, Washington, is the dominant urban center in the central interior lowland portion of the Columbia Basin. Portland, Oregon, has become the principal commercial center of the Lower Columbia Valley, with modern port facilities at the confluence of the Columbia and Willamette rivers.

Yukon River

The Yukon River, whose source lies in the mountains of western Canada, flows into the Bering Sea along the western coastline of Alaska. The drainage basin of this river occupies much of central Alaska. As a water route that crosses the vast expanse of Alaska for almost 3,200 km (almost 2,000 mi), the Yukon has offered an attractive alternative to traversing the rugged mountainous terrain of the region. When gold was discovered in Alaska’s interior Klondike region in the late 1890s, many prospectors traveled the Yukon by barge, raft, or riverboat to reach Alaska’s prosperous mining areas.

Several thousand indigenous people, who live mainly by hunting and trapping, depend on the river for transportation. Because of the region’s cold climate and limited economy, no large urban centers have developed along the Yukon. Fairbanks is the area’s largest city. It is located near the Tanana River, a major tributary of the Yukon.

Coastlines of the United States

Atlantic Coastline

The Atlantic coastline stretches 3,330 km (2,069 mi), from the northern reaches of Maine to the southern tip of Florida. While the New England region is characterized by hilly, rocky terrain, most of the remaining eastern coastline lies on a broad coastal plain, dotted with many large bays and numerous rivers. Since the outer reaches of the coastal plain are almost at sea level, it is not uncommon for extensive coastal marshes to develop in areas where fresh water from rivers mixes with ocean salt water. Sandy barrier islands parallel much of the Atlantic shoreline.

Early European colonists landed on the coast of the Atlantic. The first permanent English colony was founded at Jamestown, Virginia, in 1607. Settlements quickly sprung up along the entire East Coast. Located most commonly in the New England and Middle Atlantic states, port cities grew and became increasingly more important. Colonists shipped crops and raw materials back to Europe, in exchange for manufactured goods. Cities such as New York, Boston, and Philadelphia became distribution centers, offering supplies to pioneers traveling westward by railroad, waterways, or trails. Immigration helped to increase the population of coastal cities.

Commerce along the East Coast uses the water transportation routes of the Atlantic Intracoastal Waterway, which maintains a channel for barges and other light vessels from Boston, Massachusetts, to Key West, Florida. The waterway also utilizes rivers, bays, coastal sounds, and canals to provide a navigable route with a minimum depth of 4 m (12 ft) throughout most of its length.

Today, numerous major urban centers can be found along the entire length of the Atlantic coastline. To the south, the population of Miami, Florida, has swelled with the flow of immigrants from Latin America. In the north, the Megalopolis region is home to the largest concentration of people in the United States, stretching from Maine to Virginia. Anchored by New York City, this area also includes Boston, Massachusetts; Philadelphia, Pennsylvania; Baltimore, Maryland; and Washington, D.C.

Gulf Coastline

The Gulf of Mexico coastline extends 2,625 km (1,631 mi), from the southern tip of Texas to the southern reaches of Florida. The Spanish and French were the first Europeans to colonize the area. The United States expanded into the region in the early 19th century after purchasing Florida from Spain and Louisiana from the French. In 1845 the United States annexed Texas, which had recently won its independence from Mexico. During the westward expansion of the 19th century, New Orleans, at the mouth of the Mississippi, grew to become the most important port city on the Gulf Coast.

The discovery of large oil fields in Texas in the 1930s and the subsequent development of industry, beginning in the 1940s, spurred the economy of the Gulf Coast. Approximately 20 percent of the U.S. petroleum output comes from an area known as the Gulf Coast Petroleum Province, on the coastal plain between New Orleans, and the mouth of the Río Grande in Texas. Pipelines carry crude oil from regional and inland oil fields to many port cities. The southeastern portion of the Gulf Coast has become a major supplier of natural gas. In addition, nearly 25,000 oil and gas wells have been dug offshore, on the shallow continental shelf along the coastline.

The Gulf Intracoastal Waterway connects 9 of the 15 largest ports in the United States. This water route, primarily designed to accommodate barge traffic carrying bulk goods, consists of lagoons and canals protected by barrier islands along the Gulf Coast.

Houston, Texas, has become the largest city on the coast, with an economy based largely on oil refining. Its port is one of the busiest in the United States. New Orleans remains a prominent port city, supporting transportation of goods up and down the Mississippi River.

Pacific Coastline

Unlike other coastal regions in the coterminous United States, the 2,081-km (1,293-mi) Pacific Coast has very little flat land associated with it, except in southern California, which has a relatively smooth coastline. In other areas, the Coast Ranges plunge directly into the ocean in many places. In northern California, Oregon, and Washington, the coastline becomes increasingly irregular, consisting of a variety of bays, fjords, peninsulas, and islands.

The population along the Pacific coastline is concentrated in large urban centers. Los Angeles is the busiest port and largest city on the West Coast. Although the entire Pacific coastline is threatened by the dangers of earthquakes and violent Pacific storms, the population continues to grow. People from across the United States have flocked to the Pacific states, and immigrants from around the world, especially from Asia, have established homes in this area.

Many of the region’s coastal cities began as ports for shipping lumber or as processing locations for the fishing activities that are still important along the entire length of the coast. During the last half of the 20th century, as the focus of U.S. trade began shifting away from Europe toward Latin America and Asia, the importance of international business, shipping, and transportation functions grew in cities such as Los Angeles and San Francisco in California, and Seattle in Washington.

Alaska Coastline

The coastline of Alaska, bordering the Pacific and Arctic oceans, is 10,690 km (6,640 mi) long. Much of Alaska’s southern coastline has large bays, inlets, and prominent fjords, which were created largely through glaciation. High mountains of the Alaska Range skirt this part of the coastline, often plunging directly into the Pacific Ocean. Hundreds of islands, including the Aleutians, are concentrated off the southern coastal area. The large Yukon River delta is a dominant feature of the western coastline. The tundra landscape of the northern coastline lies on the flat Arctic Coastal Plain adjacent to the Arctic Ocean.

Much of Alaska’s economy is based on profitable offshore fisheries and on 2.2 million hectares (5.5 million acres) of commercial forests. Both of these businesses are tied directly to the coastal areas, where warm Pacific winds keep most of Alaska’s coastline ice-free year round, allowing for continuous fishing and transportation for logging operations. The Trans-Alaska Pipeline connects the oil fields of the Arctic coastal area to the southern Alaska coastline, at Prince William Sound. Approximately 1.5 million barrels of oil are transported through this pipeline every day. Most of the urban settlements in Alaska are concentrated along the coastline, with the notable exception of Fairbanks, situated in the heart of Alaska along a tributary of the Yukon River.

Hawaii Coastline

Hawaii has a coastline totaling 1,210 km (750 mi) in length. The scenic vistas and tropical beaches of Hawaii’s shores attract millions of tourists each year and have contributed greatly to the state’s economy. Because the islands are composed of fairly soft volcanic rock, which erodes quickly, the coastline is generally rocky. Areas of sheer cliffs, such as the rugged Na Pali coast on the island of Kauai, tower above the sea and beaches of white coral sand often lie tucked between the headlands. Several black sand beaches, worn from lava, dot the southeastern shore of the island of Hawaii, where the most recent lava flows meet the sea.

The scenic vistas and tropical beaches of Hawaii’s shores attract millions of tourists each year and have contributed greatly to the state’s economy. Although the coastline is extremely beautiful, it can also conceal hidden dangers. Large waves often break over the coral reefs that form just offshore of many beaches. These waves create perfect conditions for surfing, which originated in Hawaii and nearby Pacific islands, but it can also cause treacherous undertows that threaten swimmers. On rare occasions, offshore earthquakes trigger tsunamis, or giant sea waves, which can reach heights of about 9 m (about 30 ft). Tsunamis can cause extensive damage to low-lying coastal areas.

Hawaii is one of the world’s most isolated island chains. It is impossible for imports and exports to travel by land and expensive for them to arrive by air. Consequently, ships carry most of the commercial trade among the islands and between Hawaii and the mainland. Honolulu on Oahu is by far the leading port of the islands. Other important ports include Barbers Point on Oahu, Kahului on Maui, Hilo on Hawaii, and Nawiliwili Harbor on Kauai. Hawaii’s strategic mid-Pacific location also makes the island important to United States naval defense. Pearl Harbor naval base, a major military installation, is situated on Oahu.


When European settlers first arrived in what would become the United States, they found an environment rich in natural resources. Succeeding generations of Americans took full advantage of these resources. The United States became a major agricultural producer and later emerged as the world’s leading industrial nation.

As the U.S. economy developed, the nation’s natural environment changed dramatically. Farms and ranches replaced the vast forests of the North and Northeast and the wild grasses of the Great Plains. Wildlife was affected, too, as trapping, hunting, and the encroachment of human settlements reduced the populations of many indigenous animals. In the 20th century, industrial output rose sharply in the nation as urban centers expanded and the population exploded. Pollution increased correspondingly.

A movement to conserve America’s wilderness areas first gained momentum in the later half of the 19th century, and the government set aside selected areas as wilderness reserves. Little was done to address the issue of pollution, however, until the 1960s, when the deteriorating environment became a matter of intense public debate. As a result, the government took action to preserve wildlife, reduce pollution, and design policies that would lessen the impact of human activity on ecological systems. By the end of the 20th century, significant efforts at conservation and at wise management of the environment were under way. Yet at the same time a variety of complex environmental issues, many of them international in scope, still lay ahead.

Transformation of the American Landscape

Before the arrival of European settlers in the western hemisphere, Native Americans occupied the land. The earliest groups were nomadic hunters and gatherers who moved from place to place, taking advantage of the plants and animals spread over a variety of locations. The environment supplied them with the food and resources they needed to survive.

When the development of agriculture supplemented hunting and gathering among most Native American groups, they no longer had to move in search of food. Communities settled in small, permanent villages with houses constructed of local materials. Although a culture known as the Mound Builders constructed large towns centered around raised earthen platforms along the Ohio and Mississippi rivers, Native American groups seldom left permanent marks on the countryside.

European settlers, upon their arrival in North America, had a very different attitude about the environment than did Native Americans. The settlers, who founded colonies mainly along the Atlantic Coast, sought to exploit what seemed to them to be a land of plenty. They cleared trees and other natural vegetation from the land to establish farms and towns. They harvested trees to build houses and to export lumber to England. Trappers decimated the population of beaver, otter, muskrat, mink, and other animals, whose fur pelts were in high demand on European markets. By offering European goods in exchange for pelts, colonists also encouraged Native Americans to increase their take of these animals.

Almost as soon as the early colonists were permanently settled along the coast, they began moving west. Trappers and hunters usually established the first European presence in a frontier region. When they returned from western lands to the eastern colonies, they told tales of gold, silver, furs, and endless free land. These stories attracted farmers westward. They followed the routes established by trappers and hunters. As pioneers cleared huge tracts of forest, wilderness gave way to farms, cattle ranches, and organized settlements. By the mid-1800s much of the vast forest that had covered the northern and eastern regions of the nation had disappeared. On wide areas of the Great Plains, cultivated crops, such as corn and wheat, replaced natural grasses.

As human presence grew and transformed the landscape, it affected the native animal population in the United States. Trappers and hunters reduced the population of certain animal species. Animals with commercially valuable pelts decreased in number, first in the Northeast and Great Lakes region, then further west. Hunters decimated the massive herds of bison, also known as buffalo, that roamed the Great Plains, reducing the population to a small fraction of its former size. Many predatory animals, including eagles, grizzly bears (see brown bear), and wolves, declined drastically in number as their natural habitat decreased. Farmers and ranchers, seeking to protect their livestock from potential attacks, hunted and poisoned many of these animals.

Human interference with animal species also extended to offshore waters. The U.S. whaling industry, which included about 80 percent of the world’s whalers by the mid-1800s, hunted some species of whales, such as the gray whale and the blue whale, almost to extinction.

Early Conservation Movement

From colonial times through the early decades of U.S. independence, most Americans viewed the wilderness either as a dangerous, untamed region that needed to be brought under control, or as a storehouse of raw material to be exploited for commerce. Few were concerned with preserving wilderness in its natural state.

Attitudes toward nature began to change in the United States in the 1830s with the emergence of transcendentalism, a philosophical and literary movement that included writers such as Ralph Waldo Emerson and Henry David Thoreau. Among the basic tenets of transcendentalism was the belief that divinity was present in all aspects of the world and that man should treat the wonders of nature with respect and awe.

However, little action was taken to preserve the natural environment until later in the 19th century. Public concern over dwindling wilderness areas began to grow after conservationist George Perkins Marsh detailed the destruction to the natural landscape in the United States when he published Man and Nature (1864). Appreciation of areas of great natural beauty increased following an expedition by photographer William Henry Jackson and artist Thomas Moran into Wyoming’s Yellowstone area in 1871. Their depictions persuaded the public to preserve the area. In 1872 the U.S. government created Yellowstone National Park, the nation’s first national park.

In 1891 the first U.S. National Forests were set aside, but almost immediately a controversy began over the use of public wilderness areas. To some extent, that controversy continues today. The prevailing attitude in the 19th century, typified by the policies of Gifford Pinchot, first head of the U.S. Forest Service, was that wilderness areas should be used mainly as a reserve of resources for commercial use. Meanwhile, a growing number of dedicated conservationists began advocating the preservation of nature for its own sake. They pushed for restrictions on the commercial exploitation of wilderness areas.

The movement to preserve untainted wilderness areas owes much to naturalist John Muir, who dedicated considerable time to observing the wildlife, plants, and natural wonders of the United States. He worked to raise awareness among politicians and the public of the shrinking wilderness in the nation. His efforts led to the creation of both Yosemite National Park and Sequoia National Park in California in 1890. Muir also helped found one of the nation’s leading conservation organizations, the Sierra Club, in 1892. He became a close friend of U.S. president Theodore Roosevelt, who greatly expanded the national parks and national forests during the early decades of the 20th century.

Another major conservation push by the federal government took place in the 1930s following a major ecological disaster known as the Dust Bowl. For years, farmers had practiced agricultural techniques that left the land vulnerable to erosion. Many of the natural grasses that anchored the dirt had been replaced with farm crops. When a prolonged drought struck the Great Plains in the 1930s, much valuable topsoil was carried away by high winds that hit the region. In response the government instituted a number of programs to educate farmers on soil conservation techniques.

Industrialization, Urban Growth, and Pollution

Serious pollution problems did not develop in the United States until the 20th century for three reasons: a relatively small population, a modest industrial base, and the presence of only a few really large urban areas. Pollution was limited mainly to urban centers and the areas surrounding them. These areas suffered when prevailing winds dissipated fumes from industrial factories and burning trash or when rivers dispersed sewage.

The environmental situation changed dramatically in the 20th century, when both industry and population grew rapidly, causing a corresponding rise in pollution. This was particularly true of the decades following World War II (1939-1945), when many of the industrial nations of Europe were rebuilding economies damaged by the war. As one of the few developed nations to suffer almost no damage to its industrial base during the war, the United States emerged as the world’s leading manufacturing country. The nation underwent a period of phenomenal industrial growth. At the same time a major increase in population resulted from the so-called baby boom that followed the war.

Urban sprawl and roadways connecting large cities began covering an increasingly larger percentage of land once occupied by farms. Automobiles and industry polluted the air, and clouds of smog hung over major industrial centers and cities with large commuter populations. The convenient way of life demanded by Americans as the century progressed resulted in enormous mounds of solid waste. Sewage and industrial waste fouled rivers and coastal waters, particularly in the heavily industrialized Heartland and Northeast.

Growth of Environmental Awareness

Public awareness of pollution and other environmental problems began to grow during the 1960s and 1970s. Marine biologist Rachel Carson raised widespread concern about the effects of pesticides and pollution on animals and humans with the publication of Silent Spring (1962). The book suggested that a time might come when animal populations would be so reduced by exposure to pesticides that birds would no longer be heard singing in the spring.

Other events in the 1960s caused growing public concern. A number of studies began linking pollution with health problems. These studies indicated that heart attacks, emphysema, and asthma might be linked to air pollution. Scientists became aware that toxic materials in the water supply can be transmitted to humans through the food chain. A dramatic example of the effects of pollution occurred in 1969, when industrial waste caused the severely contaminated Cuyahoga River in Cleveland, Ohio, to catch on fire several times.

Growing concern over environmental problems led about 20 million Americans to take part in the first Earth Day on April 22, 1970. Citizens gathered at various events held across the country to protest abuse of the environment. Earth Day, the events leading up to it, and its aftermath helped change U.S. policy toward the environment.

Environmental Legislation

As a result of growing public concern, the Congress of the United States enacted a series of major legislative acts designed to protect the environment and limit pollution. In 1970 Congress established an independent government agency, the U.S. Environmental Protection Agency (EPA), to coordinate efforts to preserve the environment. The EPA sets environmental standards, approves state pollution control plans, and coordinates efforts with industries to clean up polluted land.

The EPA has established federal limits on air pollutants from industrial emission. It sets water quality standards and regulates regional water pollution controls. The agency also monitors radiation levels in the environment as well as the disposal, handling, and control of hazardous wastes and chemical substances, including pesticides. In addition, it conducts research to improve techniques of solid waste disposal and reuse, and to determine sources of water pollution and their effects.

The Clean Air Act of 1970 established limits on pollution levels in the air and tightened pollution emission levels for industrial factories and automobile exhaust fumes. By 1995 the emission of major air pollutants in the United States had decreased by 30 percent, even though the population had increased by 28 percent and automobile travel miles by 116 percent.

Congress also moved to improve the quality of water in 1972 with the passage of the Clean Water Act. The goal of the act was to end all pollution discharges into surface water, such as lakes, river and streams, wetlands, and coastal waters. The law also provided federal funds to help local governments construct facilities to treat sewage and remove other pollutants from water before it is discharged into the environment. Since the passage of the law, the discharge of pollutants into rivers and lakes has been greatly reduced, primarily through the construction of municipal sewage treatment plants and programs to monitor the discharge of waste from factories. Many rivers and lakes that once had only negligible animal or plant life now support healthy ecological systems. One example is Lake Erie, considered “dead” in the 1960s. By the 1990s the lake’s waters had transformed from brown to clear and a variety of fish and plant life had returned.

The government also took action to protect wildlife with the Endangered Species Act of 1973. This legislation set up provisions for identifying endangered species and prohibited the government, businesses, and individuals from harming any animal on the endangered species list or damaging its habitat. Some species have made dramatic recoveries since the adoption of the Endangered Species Act. In 1964 scientists recorded only 417 pairs of nesting adult bald eagles in the United States. By 1993, bald eagles had been removed from the endangered list and 4,016 pairs of nesting adults were known to exist. In the Southeast, hunting and habitat destruction reduced the number of alligators to the brink of extinction in the 1960s. By the 1990s, more than 1 million alligators lived in Florida.

Other endangered species have not fared as well. Conservationists are worried that the populations of some species may be so depleted that, despite conservation efforts, there may not enough genetic variety to allow these populations to continue breeding successfully. Some large predatory land mammals that need large habitat areas to survive, such as the grizzly bear and the Florida panther, are threatened as humans encroach on their territory.

Emerging Problems

During the 1970s and 1980s, research on the environment expanded and a number of previously unsuspected environmental issues emerged. The dangers of chemical waste disposal came to the forefront of public attention with incidents in communities such as Love Canal near Niagara Falls, New York, in 1979 and Times Beach, Missouri, in 1983. Developers built the communities on contaminated land that had once served as hazardous-waste disposal sites. After complaints by residents, the government declared both communities uninhabitable. In 1980 the government established what came to be known as a Superfund to clean up areas where hazardous waste had been dumped. By 1998 the Superfund had financed 500 emergency hazardous-waste cleanups at sites that presented urgent danger to public health.

Scientists also discovered acid rain, which results when pollutants combine with the moisture in the air to form acid. Winds can carry the acid clouds far from the source of the pollution before it is eventually deposited by rain. The acid rain can destroy plants and make streams and lakes unable to support aquatic life.

Other human-generated hazards have disrupted life in the United States. An oil spill in Prince William Sound in Alaska, when the supertanker Exxon Valdez ran aground on a reef in 1989, alerted the public to how fragile the northern environments are. Oil spills from offshore rigs have also polluted beaches and wetlands along the Gulf Coast. There have been problems in the nuclear energy industry as well. An accident at the Three Mile Island nuclear facility in Pennsylvania in 1979 released small amounts of radioactive gas. The accident almost resulted in a meltdown, in which radioactive fuel overheats and explodes, releasing dangerous levels of radioactive material into the atmosphere.

Environmental contamination in industrialized countries such as the United States can affect conditions around the world. In 1985 scientists observed a serious deterioration of the ozone gas layer in the earth’s atmosphere. The ozone layer forms a shield against hazardous ultraviolet radiation. The cause of ozone depletion seems to be the release into the atmosphere of chlorofluorocarbons (CFCs), chemicals once used heavily in industrial nations as refrigerants and aerosols. A thinning or disappearing of the ozone layer could damage the environment and cause medical problems for humans, particularly skin cancer.

Another potential problem surrounds global warming. Industrial development has led to increasing concentrations of carbon dioxide and other gases in the atmosphere. These gases are referred to as greenhouse gases, because they trap heat radiated by the earth, causing the atmosphere to warm. The warming of the planet’s atmosphere could have cataclysmic results. For example, accelerated melting of the polar ice caps could cause sea level to rise, increasing erosion and flooding in coastal cities, and disrupting the world economy.

Environmental Controversies

Not all Americans viewed the growing government efforts to preserve the environment as positive. Some individuals believed that environmental regulations unjustly limited the rights of individuals to use their land or prevented companies from conducting business as they saw fit. This attitude was particularly strong in western states, where the mining and lumber industries employed many people.

In the late 1970s development-minded business executives and politicians in western states organized a movement known as the Sagebrush Rebellion. Many of them supported the election of U.S. president Ronald Reagan, who took office in 1980. Reagan relaxed environmental standards, stating that the time and expense spent complying with government regulations caused undue hardships for U.S. businesses. Reagan’s environmental policies slowed a trend toward more government legislation and regulation to protect and improve the quality of the environment. Existing environmental laws remained in effect, but they were not always enforced stringently.

The Sagebrush Rebellion typified one of the most difficult issues regarding the environment: establishing a balance between economic development and environmental protection. Many people view the natural environment as a national treasure, something to be preserved for future generations. On the other hand, most Americans also want to preserve the high standard of living in the United States, characterized by high levels of consumption. The consumer culture in the United States depends on vigorous industrial output and an expanding economy to provide jobs and income. Almost all forms of economic growth have some kind of effect on the environment. Policy-makers have found it difficult to reconcile those opposing forces.

Public controversies have often emerged when environmental issues delay or cancel projects that developers claim will boost economic growth and create new jobs. For example, in 1974 the discovery of a rare fish known as the snail darter caused a four-year delay in the opening of the $100 million Tellico Dam in Tennessee. It was feared the dam would have flooded the only known habitat of the fish. Congress exempted the dam from the Endangered Species Act. Snail darter communities were later found to exist in other locations.

A similar controversy focused on the northern spotted owl during the 1990s. This rare species breeds in old-growth forests rather than second-growth forests (areas that have grown back after being cleared). In 1990s the United States Fish and Wildlife Service limited the sale of timber from areas where the spotted owl is known to nest. People in the logging industry protested, saying that the limitation prevented them from harvesting valuable timber. They compared the spotted owl episode to the snail darter controversy. Conservationists, however, pointed to the need to protect the dwindling old-growth forests, not only for the spotted owl, but also for a variety of plants and animals that live in that ecosystem.

During the 1980s and 1990s, sustainable development has emerged as the most acceptable approach to environmental problems. Sustainable development advocates policies that would allow for economic growth while at the same time minimizing damage to the environment. However, at the close of the 20th century, those who promote development and those who support environmental preservation were still working to find an acceptable balance between these contradictory goals.

A variety of organizations and community groups have taken the lead in implementing sustainable development programs in the United States during the 1990s, some of them national in scope and others local. In one of the country’s first significant efforts at sustainable development, the nonprofit Ford Foundation provided grants to communities on Virginia’s Eastern Shore, a rural peninsula of about 45,000 residents located between Chesapeake Bay and the Atlantic Ocean. The money funded programs to develop long-range economic planning, promote jobs with minimum impact on the environment, and protect the wildlife and ecosystems of the region’s barrier islands and coastal marshes.

At the same time, environmentalists on the peninsula worked closely with businesses and residents to ensure that economic prosperity and social services were not sacrificed by efforts to preserve the environment. For example, they promoted the construction of a new industrial park in the port of Cape Charles for companies dedicated to minimizing waste and pollution in their production processes. Community groups also purchased low-income rental units in rural areas and upgraded the units’ antiquated plumbing systems in order to decrease the impact of pollution from sewage.

The tax-exempt Sonoran Institute has provided assistance to communities in the western United States. Established in 1991 with technical and financial assistance from World Wildlife Fund, the institute works mainly with cities and towns adjacent to protected lands. The institute assists these communities in identifying local goals for development and environmental preservation, drawing up specific timetables and plans, and monitoring progress toward their goals.

International Issues

The United States has been involved in efforts to coordinate an international response to environmental issues that effect the worldwide environment. The most notable example is the United Nations Conference on Environment and Development, held in Rio de Janeiro, Brazil in 1992. Known as the Rio Conference, this meeting of international leaders addressed complex environmental problems. Although the participants did not reach binding agreements on all the issues raised, they made progress in a number of areas. The conference resulted in the adoption of the Framework Convention on Climate Change, an agreement to limit the amount of greenhouse gases that nations could emit. The conference also adopted nonbinding resolutions encouraging sustainable development throughout the world and urging industrialized nations to provide financial assistance to developing nations so that they could expand their economies with minimal environmental damage.

However, the United States refused to sign the Convention on Biological Diversity, which sought to protect plant and animal species and their habitats. The United States objected to provisions granting biotechnology companies access to genetic material from species around the world in exchange for a guarantee that developing nations share the benefits gained from any products manufactured from the genetic material. The U.S. government felt that the treaty did not adequately protect the rights of biotechnology companies.

The Rio Conference also revealed conflicts between industrialized nations and countries that were still struggling to develop modern economies. Many developing nations complained that nations with high levels of industrial development and consumption should not ask less developed nations to slow their industrial growth. Developing nations pointed out that they were being asked to conserve their natural resources, when developed nations, particularly the United States, were consuming a very large proportion of the world’s total resources. Many of these developing countries had large and growing populations of poor citizens. Many had few choices other than economic activities that endangered the environment; the alternative in many cases was poverty and starvation.

The U.S. Environment at the Close of the 20th Century

In the last decades of the 20th century, the United States made major strides in protecting the environment. Reductions in air and water pollution have been dramatic. Research in the United States has excelled in developing techniques to monitor the environment and in designing solutions to environmental problems. Many endangered and threatened wildlife species are rebounding, and the U.S. national park and forest systems are among the best in the world.

At the same time, major environmental problems still persist. Many of these obstacles result directly from the high standard of living that most U.S. residents have come to expect. The United States remains the world’s largest user of fossil fuels (coal, natural gas, and oil), resulting in continued generation of greenhouse gases and air pollutants. Runoff from large amounts of fertilizers used in agriculture affects the ecosystems in waterways. Solid waste disposal remains a problem, with Americans producing large amounts of trash on a daily basis. The high level of consumption in the United States encourages the wise management of natural resources while at the same time poses difficult problems involving the protection of the air, water, and land.


This is one of seven major articles that together provide a comprehensive discussion of the United States of America. For more information on the United States, please see the other six major articles: United States (Overview), United States (People), United States (Culture), United States (Economy), United States (Government), and United States (History).

© The Globe Encyclopedia. All rights reserved. Distributed by ASThemesWorld