We had to go to Gillette & looking at the map we realized Mt Rushmore wasn't much further. After all if you're headed to the edge of the earth you might as well take a detour.
It was a cool trip but it was the off-season would like to go again sometime and get some of the other areas that are mentioned in this thread.

Here's my thread with some great input:
http://www.cougarboard.com/board/message.html?id=15574428

We stayed for the lighting in the evening. It was really cool.