Deadwood Reservoir is a reservoir in the western United States, in Valley County, Idaho. Located in the mountains of the Boise National Forest about southeast of Cascade, the body on the Deadwood River is created by Deadwood Dam. The river flows south from the dam and is a tributary of the South Fork of the Payette River. The reservoir and vicinity is commonly used for camping, water skiing, fishing, canoeing, and other outdoor recreation. The full pool surface elevation is just above a mile-high at above sea level.
Approved by President Calvin Coolidge in 1928, the isolated site required substantial road building. Construction of the concrete arch dam began in late 1929 and was completed in March 1931.
Deadwood Reservoir has a dry summer humid continental climate (Köppen Dsb), with subarctic climate (Köppen Dfc) characteristics. The temperature can get hot in late July and early August. Rain and wind may frequent the area unpredictably. The climate is much like that of other high-mountain lakes in Idaho.