Constructed in 1893 by George C. Eaton and B.S. Phillips, promoters of the Sheep Mountain Tunnel and Mining Company, the Crystal Mill used a water turbine to power an air compressor. The compressor then powered tools and machinery associated with mining operations. The mill is located just outside the tiny town of Crystal, Colorado, which is only accessible by a high clearance 4×4 vehicle between Marble and Crested Butte. The mill today is a landmark for Colorado and listed on the National Register of Historic Places. Long ago when the mill was still in use, it was called the Sheep Mountain Power House at the Lost Horse Millsite, or simply the Lost Horse Mill.