Castle Rocks State Park is a 1,692-acre public recreation area in southern Idaho, in Big Cove at the base of Cache Peak in the Albion Mountains beside Sawtooth National Forest and near City of Rocks National Reserve. Known for granite formations, ranchland, and mountain scenery, it grew from protection of the former Castle Rock Ranch. The Castle Rock Ranch Acquisition Act authorized purchase of the private ranch in 2000, after which the National Park Service exchanged the land with the Idaho Department of Parks and Recreation, which began managing recreation and park facilities there on May 25, 2003. Expanded by 200 acres in 2007, it preserves habitat and public access in this distinctive landscape.