This is a great location, easy to find, about two miles located behind Mount Rushmore. It is a place where climbers will climb, so there may be a few cars that leave later in the evening, opening up a few more spots. The lot is able to hold about 25 cars. I got there on a Saturday evening at 8:30 and got one of the last few spots. Bathroom was open, and clean.

The map provided on this app wrong. where you want to end up is right outside of the pinnacles entrance for Badlands. Look that up on the map, and follow the road from this town of wall towards the pinnacles entrance and you will see it right there.