About 4 years ago we stayed at Buffalo Ridge RV "Resort" at Custer, SD. It (was then) a Good Sam campground (don't know if it still is), so we got a 10% discount for our entire stay. We stayed almost 2 weeks. We also rented a tent site for my daughter, her husband and their (then) 4 kids. We also rented one of the TeePee there for a night so the grand kids could experience something different. They have a swimming pool, play ground, and lots of space to play. They also have a dinner theater and they have a train you can ride, this is free for people camping there.
It's right there at Custer, easy drive to all the sites, including Mt. Rushmore, Custer State Park, Deadwood, Crazy Horse, all those great places. We took a driving tour through the Black Hills, Needles highway, explored all the little towns, and even went to Sturges (Full Throttle Saloon). We took an entire day to drive through Custer State Park, counted the buffalo herds, and got a kick seeing buffalo sleeping on the front porch of a house as we drove by. We went to the candy shop, the exotic pet zoo, and a lot of other places I can't even remember now.
The bottom line was ... we were so busy running all day long, every day, all we COULD use the campground for was for sleeping! There was just so much to see and do in that area.
If you are wanting a camping experience, then inside Custer State Park is your best choice.
However, we had to make reservations over a year ahead to get in at Buffalo Ridge. For this year, you are going to have a tough time finding any campsite anywhere in that area that still has any availability for 2021.
2019 Montana High Country 375FL Fifth Wheel
2014 Chevy Duramax HD 6.6 - 3500 Diesel Dully Long bed Crew Cab