USA - Geography
Across the western part of the United States extends the principal highland of North America. The land is high, rugged, and mountainous in many places. Between mountain ranges there are numerous broad plateaus stretching hundreds of miles. Through these plateaus flow rivers which cut their courses through mountain ranges amid scenes of unsurpassed grandeur. Chief among these regions are the valleys of the Columbia and the Colorado rivers.
The mountains that cross this part of the United States are the Cordilleras, the principal ranges being the Cascade Mountains and the Sierra Nevada near the Pacific Ocean, and farther inland the Rocky Mountains, whose lofty summits rise along the eastern edge of the great highland. The broadest part of the principal highland of North America occupies the western third of the United States. It measures about 1000 miles from east to west.
Along the eastern and southeastern borders of the United States is a great plain known on the east as the Atlantic Coast Plain and on the south as the Gulf Coast Plain. West of the Atlantic Coast Plain rise the Appalachian Mountains. The mountains are not so high as those in the west, but they are as beautiful in their own way. Among the most picturesque ranges are the Catskills and the Adirondacks in the state of New York, and the Blue Ridge farther south.
Between the Appalachian Mountains and the Rockies lies a broad plain, called the Central Plain. Most of the Central Plain in the United States slopes south toward the Gulf of Mexico. Through it, from north to south, flows the Mississippi River, about a thousand miles east of the Atlantic Ocean. The Mississippi River and the Rocky Mountains thus divide the United States into thirds.
The Mississippi River is a magnificent stream with several large tributaries. One of the greatest of these is the Ohio River, which rises in the Appalachian Mountains, flows down their western slope and across the narrow eastern part of the Central Plain to the Mississippi. Others are the Missouri and Arkansas, which rise in the Rocky Mountains and flow down their eastern slope. They cross the Great Plains and join the Mississippi River from the west. The Missouri River is the longest branch of the Mississippi. A small boat can go from the mouth of the Mississippi River almost to the source of the Missouri, a distance of 4100 miles. These two rivers form the longest stream of fresh water in the world.
The Red River is one of the important branches of the Mississippi. Its waters reach the Gulf of Mexico through the Mississippi, and also through the Atchafalaya and other bayous which flow through the low lying land west of the lower course of the Mississippi.
The Mississippi River and its branches are sometimes flooded on account of the enormous amount of water which pours into them, especially in the spring when they receive the water from melting snow and ice in addition to the spring rains.
The Great Lakes and their outlet, the St. Lawrence River, form the boundary between the eastern part of the United States and Canada nearly to the Atlantic, and drain the bordering portions of both countries. Between the United States and Mexico for a long distance flows the Rio Grande to its outlet in the Gulf of Mexico. This river drains large areas in southern United States and in northern Mexico.
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