Clark Canyon Dam is an earthfill dam located in Beaverhead County, Montana, about south of the county seat of Dillon. The dam impounds the waters of the Beaverhead River, creating a body of water known as Clark Canyon Reservoir. The structure was constructed in 1961-1964 by the United States Bureau of Reclamation, to hold water for downstream irrigation and for flood control purposes. Clark Canyon Dam has a crest length of , and a maximum height of . The dam contains 1,970,000 cubic yards (1,510,000 m³) of material. The elevation of the dam crest is . The reservoir has a total capacity of , and when full has a surface area of . Construction of the dam and reservoir required the relocation of U.S. Route 91 (rebuilt as Interstate 15) and a main line of the Union Pacific Railroad. The reservoir inundated the former site of the small community of Armstead, Montana, and the site of Camp Fortunate, where the Lewis and Clark Expedition camped from August 17 to 22, 1805 and held negotiations with the Shoshone. Fishing Fishing is a popular activity on the reservoir created by the dam. The reservoir is regularly stocked with fish. References External links Bureau of Reclamation: Clark Canyon Information Buildings and structures in Beaverhead County, Montana Dams in Montana United States Bureau of Reclamation dams Dams completed in 1964 Earth-filled dams 1964 establishments in Montana