The Interior Highlands

Two separate highlands regions rise above the plains in the central United States. These are the Superior Highlands and the Ozark Plateau.

Located around Lake Superior, in the northern parts of Minnesota, Wisconsin, and Michigan, the Superior Highlands are actually a part of the Canadian Shield. Coniferous forests cover rocky plateaus. There are many lakes among the hills. The Ozark Plateau is located between the Missouri and Arkansas rivers west of the Mississippi River. The land is gently rolling in places with some rugged mountains in other places.

The Rocky Mountains

West of the Great Plains is the Rocky Mountain region. The Rocky Mountains extend from Canada south to New Mexico and Western Texas. The region occupies an area over 1, 600 kilometers long, it varies in width between 200 to 600 kilometers.

The Rockies stretch from north to south. The Rocky Mountains are much more rugged and much higher than the Appalachians. Many peaks are over 3, 658 meters high. Plants are greatly affected by altitude. Mountain tops not covered by snow are capped by tundra grasses and mosses.

Intermontane Plateaus

West of the Rocky Mountains lies an area of intermontane plateaus and basins. The term intermontane means " between mountains". The region lies between the Rocky Mountains and mountain ranges along the Pacific coast.

The intermontane area is long and broad, stretching from Washington to the border with Mexico. The moun­tains block rain, and as a result, the lowland basins are dry. Some of the most impressive landscapes in the country are found in the region. The best known is the Grand Canyon.

The Pacific Coastal Ranges

The most western of the physical regions of the conterminous United States is made up of the Pacific coast mountain ranges. Like the Rockies, they extend from Canada in the north to the border with Mexico in the south. The area is about 322 kilometers wide from east to west. It has some of the highest mountains as well as some of the richest farmland in the United States.

The interior range includes the Cascade Mountains in Washington and Oregon and the Sierra Nevada in California. Within the Sierra Nevada is Mount Whitney at 4, 418 meters. Mount Rainier at 4, 392 meters above sea level, is in the Cascade Range. Also in the Cascades are active volcanic peaks. Mount Helens erupted several times in recent years. Closer to the Pacific coast is a second range of mountains stretching from Washington to California.