Several sites nestled under the trees and next to a rushing creek. Great if you want to be isolated. No water, electric and cell phones probably won't work. 

BUT, beware of Google & Bing Maps. They usually want to bring you in from the west. This part of the road is extremely rough. As in tore up the underside of my Prius to the tune of $750. OUCH!  You want to come in from the east, coming off the road between Mystic and Hill City. That road has a few places with deep ruts, but otherwise ok.

Only take the west road if you have a high ground clearance vehicle.

A primitive campground without drinking water or electricity. Fires are not allowed. There is is space for RVs and horses. It is a national park so check on pet regulations. 

The upside, Buffalo can wander through your camp. Or pose in the prairie next to the camp. Great hikes into the park.

Oh, all the things they say about being careful around buffalo, they mean it. I saw a couple who walked too close to a buffalo. Lucky for them the startled animal went away but they were in serious danger.