The 40-year statewide increases in population range from 35% in Montana to about 150% in Utah and Colorado.
The populations of several mountain towns and communities have doubled in the last 40 years.
The Great Basin and Columbia River Plateau separate these subranges from distinct ranges further to the west, most prominent among which are the Sierra Nevada, Cascade Range and Coast Mountains.
Jackson Hole, Wyoming, increased 260%, from 1,244 to 4,472 residents, in 40 years.
The rocks in the Rocky Mountains were formed before the mountains were raised by tectonic forces.
The Muskwa and Hart Ranges together comprise what is known as the Northern Rockies (the Mackenzie Mountains north of the Liard River are sometimes referred to as being part of the Rocky Mountains but this is an unofficial designation).
The western edge of the Rockies includes ranges such as the Wasatch near Salt Lake City and the Bitterroots along the Idaho-Montana border.
Within the North American Cordillera, the Rockies are somewhat distinct from the Pacific Coast Ranges and the Cascade Range and Sierra Nevada, which all lie further to the west.
The Rocky Mountains were initially formed from 80 million to 55 million years ago during the Laramide orogeny, in which a number of plates began to slide underneath the North American plate.
The Rocky Mountain System within the United States is a United States physiographic region; the Rocky Mountain System is known in Canada as the Eastern System.
The Rocky Mountains are notable for containing the highest peaks in central North America.
Farther north in Alberta, the Athabasca and other rivers feed the basin of the Mackenzie River, which has its outlet on the Beaufort Sea of the Arctic Ocean.
See Rivers of the Rocky Mountains for a list of rivers.
The United States definition of the Rockies includes the Cabinet and Salish Mountains of Idaho and Montana.