Yeah, 30 minutes at Mt. Rushmore will do it. 45, tops. Just watch North by Northwest, it's better than the real thing. As for Wall Drug, that could be a pass unless you really like tourist traps. It's just a huge store selling souvenirs in a really small town. The Main Street is pretty cool, I guess, in an old west way with saloons and ice cream parlors, if memory serves. I've been there because I was passing through, not sure if it's worth a stand alone trip but if you combine Deadwood, Rushmore and most importantly, Badlands National Park, it would be.
