narcodog wrote:
Rapid City has one of their own, across the street form one of the first fish hatchery's in the country.
Thats not Rapid City, but is located in Spearfish, the city owned campground is adjacent to the hatchery and the city park. Very nice place but possibly not large enough for the type of rally the OP is referring to as many of the sites are tight and difficult to get a large rig into. I have stayed at Spearfish, it is quite nice.
https://www.cityofspearfish.com/DocumentCenter/View/207/Campground-Map-PDFhttps://www.cityofspearfish.com/185/CampgroundRapid City has a fairground campground but it is a plain gravel area with pedestals, probably not what you are looking for.
Google map with fairground info.RV parking is in the NE corner at the corner of Centre and Campbell Streets. Looks like nearly fifty sites in 24 back to back setups.
KOA on highway 79 at Hot Springs is OK but not super fancy, has some cabins and a pavilion area. This is on the south end of the Hills and about 45 minutes from Rapid City (locals simply call it Rapid).
KOA Hot SpringsLake Angostura is a little far out, south of Hot Springs, and has about four campgrounds, all state owned.
Angostura Lake campgrounds Google MapsCharles