We stayed at a campground near the Wisonsin Dells last Fall, in Lake Delton, called Country Roads RV Park It was nice with full hookups and events at the camp store/actiivities building. When we went to Mount Rushmore. we stayed at Little Teepee Campground in Rapid City. a modest and affordable campground but clean with a friendly staff; and very convenient to all the sites. not all the sites had full hook-ups -- we had a site with electric and water only. but no problem, we used the campground bathhouse which was very clean and functional, and dumped our tanks at their dump station before leaving. While in Rapid City, if you like horses, it's well worth the trip and admission to drive down the the Wild Horse Sanctuary to see herds of wild mustangs running free on the preserve. While you're at Yellowstone, I hope you're taking a tow vehicle. We didn't and we rented a car in the town of Yellowstone -- That is one massive huge, park, we put over a hundred miles on our rental car, just going around the park. We stayed at Fishing Bridge in the park and were disappoined by this concession-run RV park -- sites were crowded too close together, sewer hook-ups were elevaed too high above ground and maeuvering around the camground was difficult, but the park itself was manificent, you quickly learn to share the roads with the herds of bison
You're welcome to look at the blog we kept of thewhole 6 month trip we made last summer. we hit so many great desitnations. I can't begin to recount them all www.greatrvescape.blogspot.com