My partner and I traveled to the Badlands area in July with our teardrop camper.  We were looking for a base campsite for which we could venture out on day trips to Badlands NP, Custer State Park, etc.  Horsethief Lake Campground was perfect!  The campground is located in the Badlands National Forest (make sure you do not mix it up with the RV Private Park Campground of a similar name) and is within a stone's throw to Mount Rushmore. (You get great views of Rushmore from the road.)

The lower loop is for RVs and the upper loop is tent camping though we did see tents down on the lower loop.  Our site #17 was ideal.  We were right on the lake with gorgeous views.  We also had access to water spigot which was right across the road. The camp hosts sell ice and firewood.  We did have some foot traffic near our site accessing the trail to the lake from the upper loop but everyone was nice.  Temperatures even in July were nice and cool and there seemed to be a constant breeze. 

I will say that the camp host was fairly cranky so check in was a little interesting.  We had read reviews elsewhere about her so we were prepared.  When we checked in, we stopped at the entrance hut and sat for a few minutes but it was unmanned.  During our trip we had experienced a lot of campgrounds doing contactless check in due to COVID precautions.  We thought this may have been the situation.   We saw the camp hosts' spot at the entrance and slowed down to see if anyone was there. It appeared to also be unmanned so we just proceeded to our site (we made advanced reservations).  We were just backing in to the spot when a 4 wheeler came zooming into the site. The camp host began berating us for "blowing through the check in".  We explained that we had sat at the hut (for 3 minutes) and did slow down at the camp host site but thought maybe they were doing contactless check in.  She then acted like we were idiots because there was paperwork to fill out.  We tried to move past that and be polite but we did see her interact with other campers in a similar manner.  This is definitely a negative which could effect your experience.  

Other than that minor challenge, I would highly recommend the Horsethief Lake Campground.  The location is convenient, the scenery gorgeous and if you are a lake person, it is a great spot to tube or lounge.