The Canadian Rockies () or Canadian Rocky Mountains comprise both the Alberta Rockies and the B.C. Rockies in the Canadian segment of the North American Rocky Mountains. They are the eastern part of the North American Cordillera, which is a system of multiple ranges of mountains which runs from the Prairies to the Pacific Coast. The Canadian Rockies mountain system comprises the southeastern part of this system, lying between the Interior Plains of Alberta and northeastern British Columbia on the east to the Rocky Mountain Trench of BC on the west. The southern end borders Idaho and Montana of the United States. In geographic terms, the boundary is at the Canada-United States border, but in geological terms it might be considered to be at Marias Pass in northern Montana. The northern end is at the Liard River in northern British Columbia.