I think I'm going to add "Climb to the highest point in all 50 states" to my to-do list.
I've already done MN: Eagle Mountain in October 2002 with RR. And on our way home from Wyoming we went to SD's High Point: Harney Peak (elevation 7242ft). It's just southwest of Mount Rushmore.
Here's a picture of the little castle thing at the top of the peak (I told you I took more pictures in Wyoming than just the car trunk).
It's about a 6 mile hike to the top and it was a beautiful day. Harney Peak is in Custer State Park. What I saw of it was nice, but we literally drove in, parked, hiked, drove out, so I'm certainly not the expert.