What mountain range forms the western border of Canada?

The Rocky Mountains form the principal western mountain range along the British Columbia-Alberta border. The Canadian Rockies stretch about 1,450 kilometres from the United States border in the south to the Liard River in northern British Columbia, with widths of 75 to 175 kilometres. The eastern edge of the Rockies (the Foothills) marks the geological transition to the Interior Plains. The range continues south into the United States as the American Rockies and forms part of the Continental Divide that separates Pacific from Atlantic and Arctic drainage.

The Canadian Rockies were formed during the Laramide orogeny about 80 to 55 million years ago, when the North American Plate collided with the Pacific Plate and pushed up sedimentary layers along thrust faults. The peaks are dominantly limestone, dolomite, and shale, eroded by glaciers during the ice ages of the Pleistocene to produce the spectacular cirque, arête, and U-shaped valley landforms seen today. The Columbia Icefield, the largest icefield in the Rockies, covers about 230 square kilometres and feeds glaciers including the Athabasca, Saskatchewan, and Columbia Glaciers.

Mount Robson in British Columbia is the highest peak in the Canadian Rockies at 3,954 metres. Other prominent peaks include Mount Columbia (3,747 metres, on the BC-Alberta border), Mount Forbes (3,612 metres), and the iconic Mount Assiniboine (3,618 metres) often called the 'Matterhorn of the Rockies'. The Three Sisters (Bow, Hope, and Faith) tower over Canmore, and the Twin Peaks of Mount Banff overlook the town of Banff. The Canadian Rocky Mountain Parks UNESCO World Heritage Site (designated 1984) covers Banff, Jasper, Yoho, and Kootenay National Parks plus three British Columbia provincial parks (Mount Robson, Mount Assiniboine, and Hamber).

The Rockies are a major tourist destination, drawing more than 4 million visitors annually to Banff National Park (founded 1885 as Canada's first national park) and 2.5 million to Jasper National Park (1907). The Trans-Canada Highway crosses the range at Kicking Horse Pass (1,627 metres) between Banff and Yoho. The Canadian Pacific Railway main line, completed at Craigellachie, BC on November 7, 1885, also crosses Kicking Horse Pass. The Rocky Mountains contain part of the headwaters of major North American rivers including the North and South Saskatchewan, Athabasca, Peace, Columbia, and Fraser. The Rockies are sacred to many Indigenous nations including the Stoney Nakoda, Ktunaxa, Cree, and Blackfoot peoples, with treaty rights and modern co-management arrangements covering the parks.