The Lewis Range is a mountain range located in the Rocky Mountains of northern Montana, United States and extreme southern Alberta, Canada. It was formed as a result of the Lewis Overthrust, a geologic thrust fault involving the overlying of younger Cretaceous rocks by older Proterozoic rocks. The range is located within Waterton Lakes National Park in Alberta, Canada and Glacier National Park and the Bob Marshall Wilderness Complex in Montana, United States. The highest peak is Mount Cleveland at 10479 ft.

Geography

The Lewis Range is within Waterton Lakes National Park in Canada, and in Glacier National Park and the Bob Marshall Wilderness Complex located in Flathead and Lewis and Clark National Forests in Montana. The Continental Divide spans much of the uppermost sections of the range. Major peaks in the range include Mount Cleveland (10,479 ft), which is the highest peak in the range and in Glacier National Park. Other prominent peaks include Mount Stimson (10,142 ft), Mount Jackson (10,052 ft), Mount Siyeh (10,014 ft), Going to the Sun Mountain, (9,642 ft) and the isolated Chief Mountain (9,080 ft). The Chinese Wall in the Bob Marshall Wilderness is a 1000 ft high feature that runs for 40 mi. Major passes include Marias Pass and Logan Pass which bisects Glacier National Park east to west.

Geology

Formed by the Lewis Overthrust beginning 170 million years ago, an enormous slab of Precambrian rocks 3 mi thick, 50 mi wide and 160 mi long faulted and slid over newer rocks of the Cretaceous period. In this relatively rare occurrence, older rocks are now positioned above newer ones.