What are the Rocky Mountains?

The Rocky Mountains are the major mountain range of the western United States and Canada, extending about 3,000 miles from northern British Columbia and Alberta in Canada south through Idaho, Montana, Wyoming, Colorado, Utah, and New Mexico in the United States. The range varies from 70 to 300 miles wide and reaches more than 14,000 feet in elevation in Colorado. The Rockies form the eastern edge of the Cordillera, the great mountainous spine of western North America.

The Continental Divide of the Americas runs along the crest of the range, separating waters that flow east toward the Atlantic and Gulf of Mexico (via the Mississippi-Missouri system, Rio Grande, and Arkansas) from waters that flow west toward the Pacific (via the Columbia, Colorado, and Snake rivers). The highest peak in the U.S. Rockies is Mount Elbert in Colorado at 14,440 feet, although Mount Massive (14,428) and Mount Harvard (14,421) are nearly identical. Colorado contains 53 named peaks above 14,000 feet (the so-called Fourteeners). Other major peaks include Pikes Peak (14,115 feet) near Colorado Springs, Long's Peak (14,259) in Rocky Mountain National Park, and Grand Teton (13,775) in Wyoming.

The Rockies were uplifted during the Laramide Orogeny between roughly 80 and 55 million years ago, with subsequent erosion exposing the granite cores of the higher peaks. Glaciation during recent ice ages carved the dramatic peaks, lakes, and U-shaped valleys characteristic of the higher Rockies. The range divides the Great Plains to the east from the Great Basin and Colorado Plateau to the west.

Notable national parks in the U.S. Rockies include Rocky Mountain National Park (Colorado), Grand Teton (Wyoming), Yellowstone (Wyoming, Montana, Idaho), Glacier (Montana), and Great Sand Dunes (Colorado). The Rockies are home to wildlife including grizzly bears, black bears, elk, moose, mountain goats, bighorn sheep, mountain lions, wolves, lynx, and many smaller species.

Indigenous peoples including the Ute, Shoshone, Crow, Blackfoot, Arapaho, Cheyenne, and Apache lived in and around the range for centuries. The Lewis and Clark Expedition crossed the Rockies through the Bitterroot Mountains in 1805. The range was a major obstacle to nineteenth century westward migration, with passes like South Pass in Wyoming becoming critical routes on the Oregon and California Trails. The Transcontinental Railroad completed May 10, 1869 crossed the southern Rockies at Sherman Pass in Wyoming.

Mining booms in Colorado, Idaho, and Montana from the 1850s onward built towns including Denver, Boise, Salt Lake City (technically just west of the Wasatch), and Boulder. The Rockies remain economically important for tourism, recreation, ranching, mining, and forestry, and they contain headwaters of rivers that supply much of the western United States with water.