Rafter J Bar Ranch, Hill City, SD ... http://www.rafterj.com
... is a great place. Well maintained, large spaces not close to one another, other amenities. 27 mi. SW of Rapid City, SD on US Hwy 16. 12 mi further south, then back East on State Hwy 244 to Mt. Rushmore. We loved it there...good motorcycle riding; good hiking in, around and surrounding the RV park.
Our second choice was the Mount Rushmore KOA, 12620 Highway 244, Hill City, SD 57745.
Check out: RV Park Reviews :: Hill City, South Dakota ( SD ) - RV Parks and Campground Reviews
Enjoy! It's a great place to go RVing.