Kootenai Falls is a waterfall on the Kootenay River located in Lincoln County, Montana, just off U.S. Route 2. It is the largest undammed waterfall in the state and one of the largest waterfalls in the United States by flow rate. The falls is accessed by a foot trail from the parking area next to the highway. The area's ecology includes large animals such as bighorn sheep and American black bears, while the geology includes compressed, folded sandstone and shale dating back millions of years, with visible remnants of algae mats and water marks from when Montana was covered by water.