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The topography of the United States varies considerably from place to place.The continental U.S.can be roughly divided into three basic geographic areas：the Atlantic coastal region and the Appalachians in the east，the great Mississippi River Basin in the middle，and the mountainous region in the west stretching to the coast of the Pacific Ocean.Each of these areas includes a large amount of geographical diversity.
The Atlantic coast of the United States is about 3，330 kilometers long from Maine in the north to Florida in the south.In the northern part，the coast is very rugged and rocky，but has some very good deep water harbors which are important to trade.Inland from this coastline lies the region known as New England，which includes six states：Maine，New Hampshire，Vermont，Massachusetts，Rhode Island and Connecticut.This region is full of low mountain ranges，rolling hills and small streams.As the soil is rocky，relatively few large⁃scale farms have developed there.
The Coastal Plain refers to the relatively flat area between the Atlantic coast and the Appalachian Mountains.The Coastal Plain begins south of New England，and is narrow in the north and wide in the south.The region south of New England is known as the Mid⁃Atlantic region，and includes six states：New York，Pennsylvania，New Jersey，Delaware，Maryland and West Virginia.This region is good for agriculture as the land is flat and the soil is fertile.
The coastal region south of the Mid⁃Atlantic region is part of the area commonly known as the South.It includes Virginia，North and South Carolina，Georgia，and Florida.In Georgia and Florida，the Atlantic Coastal Plain meets the Gulf Coastal Plain，which is adjacent to the Gulf of Mexico.The Gulf Coastal Plain stretches west to the Mexican border and north to Arkansas.Generally speaking，the soil of the coastal plains is rich and productive although large parts of Florida are swampy.
To the west of the Atlantic coastal plain lie the Appalachian Mountains.They begin in Quebec，Canada and extend 2，400 kilometers southwest to northern Alabama.The Appalachians are quite old and not very high;the highest peak is only 2，037 meters above sea level.Nonetheless，the Appalachians presented many obstacles for early Americans who sought to move west.They are heavily forested and the many valleys in the mountains are fertile，although they are not easily accessible.
The vast area between the Appalachians and the Rocky Mountains contains the Central Lowland of the Mississippi Valley，and the Great Plains that lie to the west.
The Central Lowland was originally covered by glaciers during the most recent ice age that ended about 10，000 years ago.Repeated glacial advance and retreat eroded the land and created many lakes，the largest of which are the Great Lakes in the northern part of the United States.The glaciers also left behind a thick layer of rich soils that makes the land very flat.Visitors sometimes complain that the landscape in this region is boring because of the lack of variety.However，the loess makes the soil very fertile.As a result，this area contains some of the most productive agricultural regions in the country.
The large area between the Central Lowland of the Mississippi Valley and the Rocky Mountains is known as the Great Plains，covering an area of 1.4 million square kilometers，about 15％ of the nation’s territory.There are very few trees in this region.The plains used to be covered with tall grass，but people have turned the fertile areas into agricultural land，although the dry climate limits farming to a limited number of crops such as wheat，corn and sorghum.Cattle ranching is also important，especially in the western parts of the region.
In the past，soil erosion was a serious problem in the southern Plains due to overgrazing and careless plowing.When serious droughts occurred，the loose dry soil would be blown away.In the 1930’s，this led to giant dust storms which led people to call the region the Dust Bowl.Many farmers at the time were forced to leave their homes and move west.The government then introduced soil conservation policies to help farmers prevent erosion，but smaller dust storms still sometimes return during extremely dry weather.
The area west of the Great Plains is very mountainous.These mountains are part of a great continental chain of mountain ranges that stretches from Central America through Mexico，the western United States and western Canada to Alaska.In the United States，the western region includes several mountain ranges：the Rocky Mountains（also known as the Rockies）lie furthest inland，the Cascades and the Sierra Nevada（also known as the Sierras）are in the middle of the mountain region，and the Coastal Range is on the Pacific Coast.
The Rockies are a comparatively young mountain range and are much higher than the Appalachian Mountains in the east;many of the peaks are more than 4，000 meters above sea level.The Rockies are not an unbroken mountain chains，so they did not present an overly difficult obstacle for settlers traveling west in the past.
West of the Rockies are the Cascades in Washington State and Oregon，and the Sierras in California.The Cascades are full of beautiful snow⁃covered volcanoes.South of the Cascades the Sierras，which are extremely rugged and spectacular，and which hold many mineral deposits such as gold and silver.
The large region between the Rockies to the east and the Cascades and Sierras to the west is called the Great Basin.The famed Death Valley is part of this region.Most of the valley is below sea level，and it is the site of the lowest point in the Western Hemisphere at 86 meters below sea level.The valley is surrounded by mountains and is extremely hot in summer，reaching above 50℃.
West of the Cascades and the Sierra Nevada Mountains，and east of the Coastal Ranges are three large valleys which contain some of the nation’s richest farmland.In the north，the Willamette Valley in the state of Oregon is known for its very fertile soil which is used to grow wheat，fruits and vegetables.Most of the population of Oregon lives in this region.To the south lies the Central Valley of California，which is considered the richest farmland in the entire American west.Further south near Los Angeles is the Imperial Valley，where much of America’s winter vegetables and citrus fruits are produced.
The Coastal Range is a chain of low mountains on the Pacific Coast stretching from Southern California to Washington State.The presence of these mountains near the sea makes the California and Oregon coasts extremely rugged and beautiful.
Generally speaking，the entire mountainous western region has a great amount of very striking scenery.Many national parks are located here，including Yellowstone National Park，Grand Canyon National Park，and the Yosemite National Park.Yellowstone National Park encompasses 9，000 square kilometers of land in Wyoming，Idaho，and Montana.Its landscape includes canyons，waterfalls，lakes，volcanic plateau，rugged mountains，geysers，hot springs，rivers and forests.The Grand Canyon，created through erosion by the Colorado River，is located in northwestern Arizona.It measures up to 29 kilometers across at its widest point.The West also has many designated national forests，the most famous of which are the giant sequoia trees in California.