Rocky Mountains

segment of the Rocky Mountains, extending southeastward for about 1,000 miles from northern British Columbia, Canada, and forming nearly half the 900-mile border between the provinces of British Columbia and Alberta. The Mackenzie and Selwyn mountains farther north along the border between the Northwest and Yukon territories are often included in the Canadian Rockies. To the west, the Rocky Mountain Trench (a geologic depression) separates the front ranges of the Canadian Rockies from the Columbia Mountains, which include the Cariboo, Selkirk, Monashee, and Purcell mountains and are also often considered part of the Rocky Mountain system.