United States Geography

B8

c

Population

In the 1990s approximately 70 percent of the population of the Great Plains lived in scattered urban areas. Denver, Colorado is by far the largest city of the region, with a metropolitan population of 1.9 million people in 1997. It lies along the western boundary of the region. Denver is a diversified city, serving as a market and industrial center for both the Rocky Mountain region to the west and the Great Plains. Other large urban centers include San Antonio, Texas; Tulsa, Oklahoma; and Wichita, Kansas. These cities serve as regional trading centers for surrounding areas.

B

9

The Rocky Mountains

The Rocky Mountains region can be characterized as an area of breathtaking scenery, rugged terrain, scanty resources, and scattered population. The boundaries of this region are fairly precise, as the sharp relief of the frontal ranges contrasts with the relatively flat Great Plains region to the east. To the west, the Rocky Mountains region is bordered by the plateaus and basins of the Intermontane region. The northern boundary of the U.S. Rockies is considered the Canadian border, although the mountains physically stretch well into Alberta and British Columbia. In the south, the mountain range ends north of Albuquerque, near Santa Fe, New Mexico.

B9

a

Natural Features

The Rocky Mountains were formed relatively recently in geologic time. During the Cretaceous Period, from approximately 135 million to 65 million years ago, a saltwater extension of the Gulf of Mexico covered most of this region, as well as the Great Plains. A deep layer of sediment, perhaps as much as 6,000 m (20,000 ft) thick, covered the granitic rocks that now form the Rocky Mountains. Finally, a series of crustal uplifts, accompanied by large-scale erosion, created the mountainous terrain that exists in the region today. .

These block-faulted mountains are young compared with many of the world’s other mountains. They are characterized by a complex system of troughs and ridges that are a result of tectonic uplift and subsidence of adjacent blocks of the earth's crust. Other features of the area’s landscape have been shaped through glaciation. Many of the major rivers of the western United States, including the Columbia, Fraser, Missouri, Colorado, Arkansas, Rio Grande, and Snake, originate in the upper elevations of the Rocky Mountains.

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B9

b

Economy

Although irrigated farming, livestock ranching, and lumbering offer limited economic opportunities within the region, the two major commercial activities in the Rocky Mountains are mining and tourism. Small mines are scattered throughout this region, but several have achieved major significance at one time or another. Major finds of gold, lead, zinc, and silver were discovered around Leadville, Colorado, particularly in the last quarter of the 19th century. Today, Leadville continues to be a mining center and is the home of the Climax mine, which employs over 3,000 workers. This mine is the world’s largest producer of molybdenum, which has a very high melting point and is used to make the heat-resistant steels used in automobiles, aircraft, and various commercial and industrial appliances. The Coeur d’Alene area of northern Idaho also continues to be a productive mining center, producing substantial quantities of silver, lead, and zinc.

Tourism is based on abundant natural attractions and outdoor recreation and has become the most vigorous part of the region’s economy. Resort communities have been established to cater to the region’s tourist industry, and their population often grows exponentially during peak tourist seasons. Skiing is the dominant winter season activity. Major destinations are Aspen, Vail, Keystone, Breckenridge, and Copper Mountain in Colorado, as well as Sun Valley in Idaho and Snowbird in Utah. In the summer, tourists flood the region to visit points of interest, such as Pikes Peak, Royal Gorge, Rocky Mountain National Park, Yellowstone National Park, Grand Teton National Park, and Glacier National Park.

B9

c

Population

There has been little urban development in the Rocky Mountains. Throughout history, the population of the area has been very sparse. Many of the permanent settlements are tied to economic activities such as tourism, forestry, mining, and agriculture. Populations in these locations often vary with economic conditions. For instance, the number of people living in some communities often fluctuates with changes in mining productivity or according to seasonal cycles of employment in the tourism industry. In the late 1990s there were fewer than 4 persons per sq km (10 people per sq mi) and few cities within the area have populations greater than 50,000 people. The one city that exerts the most influence within the region is Denver, Colorado, which is not actually located within the region, but lies at its eastern edge. Denver serves as a commercial, industrial, and distributing center for the Great Plains as well as the Rocky Mountains.

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