Day 3 from Road trip 2016:
Temperatures were pleasantly cool overnight on night #2 and the breeze was high enough to keep the bugs down so outdoor sleeping conditions were excellent. I woke up after the sun crested the nearby ridge, had breakfast, and loaded up for a drive through Badlands, then onto Mount Rushmore for lunch, and dinner/camp at Devils Tower in Wyoming.
Badlands is incredible and I hit a couple of little side roads for a bit of exploring, but breaking out on foot will get you better access. I stopped off at the world (in)famous Wall Drug because, you kind of have to after driving so far... at least once.
Mt. Rushmore was ok and I'm glad I went to see it, but it was very touristy and more or less just an expensive observation deck. Devils Tower on the other hand was an epic natural feature that keep looming up in the distance for miles and miles during the approach. There's a loop hike around the base that's definitely worthwhile and a great KOA campground with flush toilets, showers, and (spotty) WiFi right outside the park - I camped there for the night and hiked Devils Tower the next morning.