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The United States lies in North America with its two youngest states—Alaska on the northwest tip of the continent and Hawaii in the central Pacific.The continental United States stretches 4，500km.from the Atlantic Ocean on the east to the Pacific Ocean on the west.It borders Canada on the north，and reaches south to Mexico and the Gulf of Mexico.Its coastline runs 19，924 km.The total area of the United States is 9，372，610km²，which makes it the fourth largest country in the world.

So far as the geographical features are concerned，the large territory of the continental United States can be divided into three basic areas.

Along the Atlantic Seacoast is a narrow plain that begins far up to the coast and becomes wider as it goes south.The coastline of New England¹ is lowland made up of sandy beaches，swamps，lakes，and gently sloping hills.The interior contains mountains，rivers，rocky hills，and valleys.The land here is generally infertile and much of it is covered by heavy forests.The coastline，however，is broken by many excellent harbors that were once important centers of commerce and trade in the early days of the country.The Middle Atlantic States，consisting six states（New York，New Jersey，Pennsylvania，Maryland，Delaware，and West Virginia），is a flat and fertile region.It is the most densely populated region of the United States，and famous for its great cities and ports，its financial and foreign trade activities，its cultural and educational centers，and its factories and mines.Many heavily wooded mountains and deep valley cut by wide and beautiful rivers can be found here.Three important rivers，the Hudson，the Delaware and the Susquehanna，flow through this part of country.In the Deep South²，the coast plain is very low and wide.The soil of this region varies greatly.Some parts along the coast are almost pure sand.Other sections contain some of the richest soil in the whole country.However，the rivers，fertile plains，and mild temperatures of the South make it suitable for large-scale agriculture.

To the west of the Atlantic coastal plain lie the Appalachian Mountains that begin in Canada and reach all the way to Georgia and Alabama.These are old mountains with rounded tops and wooded hills，usually not exceeding 800 m in height.The highest point is only 2，000mabove the sea.Most of the mountain ridges are low enough to be easily crossed by modern highways.The Appalachians have much beautiful scenery and many tourist resorts.The Ohio and the Tennessee Rivers flow down the western slops of the Appalachians to the great Mississippi River，deep in the heart of America.

The Mississippi River Basin between the Appalachians and the Rockies is one of the largest areas of flatland in the world，which takes up about half of the continental United States，and covers a distance of some 2，000 km in width.Through the center of this vast land runs the mighty Mississippi，the most important and longest river in the US.It flows about 6，400km from its northwestern source in the Rockies to the Gulf of Mexico.

The northeastern part of the Mississippi River Basin is called the Midwest，or the Middle West.It lies in the general area of the Great Lakes³.From east to west，the states in the Midwest are Ohio，Michigan，Indiana，Illinois，Wisconsin，Missouri，Iowa，and Minnesota.This region has great mineral resources，rich soil，agood climate for agriculture，fertile plains，low rolling hills，and no high mountains.Many rivers flow through this area.Among the five Great Lakes only Lake Michigan is wholly in the United States.The other four are shared with Canada.These five lakes cover an area of 245，300km² and are the largest group of freshwater lakes in the world.

The large area between the Mississippi and the Rockies is called the Great Plains.It covers，from north to south，six states：North and South Dakotas，Nebraska，Kansas，Oklahoma，and Texas.The land in this region is very flat and open.Except for a few widely separated sections，there are no trees or forests in this whole region.The soil here is generally fertile，but the dry climate limits farming to a few important crops.Wheat and corn are main crops in the plain states.But in the west sections，cattle raising is more important.

To the west of the Great Plains lie the Rocky Mountains，“the backbone of the continent”.These high mountains stretch all the way from Mexico to the Arctic and form what is known as Continental Divide，or Great Divide，the most important watershed on the continent.The Rockies are more than twice as high as the Appalachians and high enough to receive more rain than the surrounding plains and plateaus.Consequently，they are mostly forested.The striking and varied scenery of the Rockies has given rise to the establishment of many national parks here.The most famous one is the Yellowstone National Park which covers an area of about 9，000km².It is in the northwest corner of Wyoming，but also takes up part of Montana and Idaho.There are about 3，000geysers and hot springs in the park.The other natural wonders include roaming herds of buffalo，elk，deer，antelope and sheep，as well as the famous grizzly bear.

Between the Rocky Mountains and the Cascade-Sierra Nevada ranges is the great plateau area.The land here is arid and often very sandy.Generally，it serves no agricultural purpose.The Great Basin between the Sierra Nevada Mountains and the Rockies is particularly dry and much of it is desert.Death Valley is on the western edge of this region.The valley，200km long，5to 40 km wide and 86mbelow the sea level，is the lowest and hottest place in North America.The Cascade-Sierra Nevada range is very high and contains many peaks，one of which is Mt.Whitney in southern California，4，397mhigh—one of the highest points in the United States.

Along the Pacific coast from Washington State to southern California，extend the Coast Ranges.Between the Cascade-Sierra Nevada range and the Coast Ranges there are fertile valleys.The Central Valley of California，for example，is a highly productive area extending more than 800km from northwest to southeast.The area produces enormous amounts of fruits and vegetables.It is also important for such basic field crops as sugar beets，beans，rice，and cotton.