We traveled from Sioux Falls to Wall, South Dakota and hit some tourist traps on the way. We saw the Corn Palace in Mitchell which was interesting, we stopped to see a Lewis and Clark keel boat which wasn't really a boat, and we stopped at Wall Drugs. Wall Drugs has an interesting story (wiki it) but it is a king size tourist trap. Lots of shops, a few interesting historical photos and lots of shops. If you are going on I-90 in South Dakota, give it a try. Don't go out of your way to see it.