We stayed at Hidden Valley RV Park near Deadwood.
http://www.hiddenvalleydeadwood.com
Lovely park. We had a site right on the creek with a deck off the side of the trailer. The bathrooms/showers were spotless. Sites for large rigs. We were so early in the season that we woke up our second morning with four inches of snow on the ground.
If you are into wine tasting, the Prairie Berry winery in Hill City has some very interesting wines. No fee for their tastings, either. The Red Ass Rhubarb wine is outstanding. I don't normally like fruity wines, but this tasted like rhubarb cobbler!