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 resulted in 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 .