II Major Rivers, Lakes and Mountains

Rivers

●Mississippi River

The Mississippi River, lying between the Appalachian Mountains and the Rocky Moun-tains, is the most important river in the United States and one of the great continental rivers in the world. It flows 3,770 kilometers from its source in northwestern Minnesota to its mouth in the Gulf of Mexico.

The Mississippi is the largest river in North America. This means that it carries a greater volume of water than any other North American river. But the Mississippi is not the longest river. That honor goes to the Missouri. The Missouri is 320 kilometers longer. But if Mississippi is measured from the source of its chief headstream（the main branch）, the Missouri River, it is over 6,000 kilometers with more than 40 tributaries. The two major tributaries are the Missouri River and Ohio River. The Illinois and Arkansas are other major rivers that flow into the Mississippi. Along the way, the Mississippi borders ten states. It is known as the Father of Waters.

●Missouri River

The Missouri River is the longest river system in the United States. It flows about 4,090 kilometers from southwest Montana among the Rocky Mountains to just north of St. Louis, Missouri, where it joins the Mississippi River. The river is nicknamed“The Big Muddy”as it has a great deal of mud in it. On its way to the Mississippi, the Missouri forms part of the border of seven states. The three largest cities along the Missouri are Omaha in Nebraska, and Kansas City and St. Louis in Missouri.

●Ohio River

Another main tributary of the Mississippi is Ohio River（1,500 kilometers）, which rises from the rainy east at Pittsburgh, Penn. and joins the Mississippi at Cairo, Illinois. It served as the gateway to the West at the beginning of the 1800s for the early settlers moving west from the Appalachians. By the 1820s, steamboats had arrived on the Ohio River. Steamboats moved a lot faster than flatboats. Traffic on the Ohio rapidly increased as steamboats carried goods and people up and down the river. Three cities became important centers of trade because of their locations on the busy waterway: Pittsburgh, Cincinnati（in Ohio）, and Louisville（in Kentucky）. Traffic on the river lessened in the late 1800s after the railroads were built.

By the mid-1900s, the Ohio River had become severely polluted. Sewage and industrial wastes had been dumped in it for many years. No one wanted to swim in the river. Cleanup efforts have helped make the river a place where people can once again enjoy fishing, swimming, and boating.

●St. Laurence River

Another important river is the St. Laurence, which forms part of the boundary between Canada and the United States. The St. Lawrence River is the chief outlet of the Great Lakes, flowing northeast from Lake Ontario to the Gulf of St. Lawrence on the North Atlantic Ocean, a distance of 1,300 km. It serves as a major water route to the interior of the United States and Canada, linking the Great Lakes with the Atlantic Ocean.

●Colorado River and Columbia River

On the Pacific side there are two great rivers: the Colorado River and the Columbia River. The Colorado River begins in the Rocky Mountains. It flows southwest for some 2,300 kilometers and empties into the Gulf of California. For 342 of these kilometers the Colorado flows through the magnificent Grand Canyon in Arizona, which is one of the most beautiful places in the United States. The Colorado drains an enormous area. All the farms and cities of the southwestern corner of the country depend on its water. Many Dams have been built in the Colorado River system. Hoover Dam, built in 1936 by the federal government, is the largest of the dams located on the Colorado River.

The Columbia River rises in western Canada and continues in the US for about 1,900 kilometers. It flows into the Pacific Ocean. The volume of the Columbia's flow is second only to that of the Mississippi. among the US rivers.

●Rio Grande River

Another important river in the southwest America is the Rio Grande River. It runs about 3,000 kilometers from the southern Rocky Mountains to the Gulf of Mexico and forms part of the United States-Mexico border.

●Rivers East of the Appalachians

The rivers east of the Appalachians are usually short. All of them run to the Atlantic Ocean. The Potomac River is famous not only because Washington D.C. is located on its band but also because it is the dividing line between the South and the North. The Hudson River is famous because New York City stands at the river mouth. It is there（at New York City）that the Hudson river meets the Atlantic Ocean. Linked by canals with the five Great Lakes, the Hudson River serves as an important route for inland waterway traffic.

Great Lakes and Niagara Falls

●Great Lakes

Along the United States-Canadian border lie the world's largest group of freshwater lakes—the five connected Great Lakes, including（from largest to smallest）Lake Superior, Lake Huron, Lake Michigan, Lake Erie, and Lake Ontario. The lakes are a part of both countries and are shared by both. Only Lake Michigan lies entirely within the United States.

Covering an area of 244,100 square kilometers, the Great Lakes are so large that they could be easily seen from the Moon! All together, the lakes hold about 20 percent of all the fresh water on the Earth's surface. The Great lakes are connected to the Atlantic Ocean by the St. Lawrence River. Four of North America's largest cities are located on the edge of the Great Lakes. They are Chicago, Detroit, Toronto（Canada）, and Cleveland. These lakes are joined together by canals and linked to the Mississippi. and its tributaries. They are the economic lifeline of the Midwest.

●Niagara Falls(尼亚加拉瀑布)

Niagara Falls is the most spectacular falls in the United States because of its great beauty and immense size. It is part of the Niagara River, which connects Lake Erie and Lake Ontario. East of the river is the United States. West of the river is Canada. About halfway between the two lakes, a sharp drop in the river makes Niagara Falls.

Niagara Falls consists of two giant waterfalls and one smaller one. One big waterfall, called American Falls, is on the US side of the river. The waterfall is 328 meters wide and 55 meters high. The biggest of the two giant waterfalls is in Canada and is known as the Canadian Falls, also called the Horseshoe Falls because of its horseshoe shape. The curved edge of the Canadian Falls measures 670 meters wide and the water drops 57 meters. The Canadian Falls carries nine times more water than the American Falls! A great tourist attraction, Niagara Falls makes an enormous, ground-shaking roar and a huge cloud of water mist. Rainbows shine through the mist. At night, the falls are lit with colored lights, creating a brilliant display!

●Great Salt Lake

In northwest Utah lies the Great Salt Lake. Its maximum depth is 8 meters. As a terminal lake, the Great Salt Lake is several times more saline than seawater, making it easy to float in. It contains about 4.4 billion tons of minerals. About three fourths of this total is common table salt. Surrounded by stretches of sand, salt land and marsh, the lake remains isolated, though in recent years it has become important as a source of minerals, as a beach and water-sports attraction, and as a wildlife preserve. Near Great Salt Lake lies the capital and largest city of Utah—Salt Lake City. The marshlands on the lake's eastern and northern shores are the habitat for millions of migratory shorebirds and waterfowl.

Mountains

Beside the Appalachian Mountains and the Rocky Mountains, there are still a few more worth mentioning in this part. Mount McKinley in Alaska is the tallest mountain in the United States. It rises 6,194 meters above sea level. In the Sierra Nevada of eastern California, Mount Whitney, at 4,418 meters, is the highest peak in the United States outside of Alaska. The Sawatch Mountains form part of the Continental Divide, which runs through western Colorado. The divide, the main watershed boundary of the North American continent, weave（迂回通过）through the continent along the tops of the Rocky Mountains. It marks the point at which all rivers to the east flow toward the Atlantic Ocean and all rivers to the west flow toward the Pacific Ocean. The Cascade Range is a major mountain range extending from northern California through Oregon and Washington into British Columbia, Canada.