I'm going to be driving from Aspen to Chicago next week and since I've never been to Mt. Rushmore I thought it might be nice to go that way. I'm going through Cheyenne, WY and Sioux City, SD on my way and I was wondering if there's anything worth doing some sightseeing for in either city. I cannot venture out, as I'm on a time limit, so I have to stick to the route and interstate. However, I would have a few hours that I could look around both cities. Any suggestions are welcome! Thank you in advance.