Sofa Mountain is a 2,515-meter summit in Waterton Lakes National Park, Alberta, in the Lewis Range of the Canadian Rockies. It is the easternmost mountain in both the park and the Canadian Rockies, and its north face rises dramatically more than 1,220 meters above Middle Waterton Lake over about six kilometers. The name originated in 1865, when Kootenay Brown likened it to a sofa-like peak among the clouds, and it was formally adopted in 1943. Formed from sedimentary rock laid down between the Precambrian and Jurassic, the mountain was shaped by the Lewis Overthrust beginning about 170 million years ago, and its runoff feeds the Waterton and Belly rivers.