Horsethief Lake is Heaven
This campground is amazing. The only drawback is that it does not have flushing toilets or a shower, BUT, the views are beautiful. The campground is nestled into the forest right next to the lake. It is only two miles from Mount Rushmore, so if want flushing toilets they are only a short car ride away. There are spots for camper trailers as well as plenty of tent sites.
Horsethief Lake trail is about 3 miles long and the trailhead is right at camp. It is an easy hike that puts you right in the middle of the Black Hills. If you are more adventurous the trail connects to the Centennial Trail which is 111 miles long.
This campground is five stars even though it doesn't have flushing toilets or showers. This campground used to be first come first served only but it now has some reservable sites on ReserveAmerica.com.