Deerfield Dam is a dam impounding Castle Creek in the Black Hills of South Dakota. The dam creates Deerfield Reservoir within the Black Hills National Forest. The earthen dam was originally built by the United States Bureau of Reclamation in 1942–1947, with a height of 171 feet, to store irrigation water for the surrounding Pennington County. Construction was started in July 1942 by the Farm Security Administration, and later continued by the Civilian Conservation Corps under the Works Projects Administration during World War II. Employment of conscientious objectors under the Civilian Public Service here drew complaints from locals.