Crystal Mill is a wooden powerhouse above the Crystal River in the former mining settlement of Crystal, Colorado, and one of the best-known remnants of the region’s late 19th-century mining era. Built in 1893 by George C. Eaton and B.S. Phillips for the Sheep Mountain Tunnel and Mining Company, it powered the Sheep Mountain Tunnel by using water-driven machinery to run an air compressor for nearby silver-mining tools and equipment. Though often called a watermill, it functioned as a compressor station and was long known by industrial names tied to the Lost Horse Millsite. Its working life ended in 1917, and it later became a preserved landmark listed on the National Register of Historic Places in 1985.