There is a statepark next to Badlands trail rides, but they have their own campground. We had the Riverview site. It had electricity and free firewood and the most incredible view of the badlands. We didn't realize there were no water hookups here. They had a cooler of drinkable water and a jug of non-potable water. If we had known, we could have filled up at the bathrooms. But it was an incredibly tight drive to the site through a gate. Nice people. Just ask a lot of questions before you go. We camped here in a Travel Trailer.
None of the web sites/books we use showed this park as having camping, nor were there blue RV signs along the highway. However, a ND Dept. of Tourism brochure said this park had RV camping, so we took a chance because we needed to escape the high winds (50mph sustained!). We traveled down a washboard-y dirt road, wondering what we were getting into, then we saw it--gorgeous badlands and a very tidy horse camping park. Lots of corrals and horse trails. The camp host could not have been friendlier or more helpful. Fee is $12 to camp plus $5 ND day use/vehicle fee. Not bad. And the views are just spectacular. There is a picnic pavilion, a fresh water pump (not threaded), a dump station, and lots and lots of trails. They are currently building what looks to be a very nice showerhouse/bathroom. Until that is completed, come self-contained as it's primitive. And bring leveling blocks--just grass lawn to park on. With all those caveats, though, we really enjoyed this little park. Very quiet and highly unusual. We would stop here again and next time rent a horse to go on more of those trails! (Please note: Number of campsites is just a guess. None of the ND literature or web sites says how many sites there are.) We camped here in a Motorhome.