Not much else to mention, all good suggestions.
If you are age 62 or over, by all means get your senior America the Beautiful Pass. If not 62 a annual America the Beautiful pass is worth the $80. Badlands alone is $20. Devils Tower is another $20.
At Chamberlain, SD where I-90 crosses the Missouri River, if you travel north a few miles to Ft. Thompson, there is a COE campground below the dam in the middle of the river (like the one in Pierre) and it is super nice. I stayed there when I saw I was not going to make the Badlands campground.
Also, in Rapid City (know to locals simply as Rapid) there is a museum called the Journey. Well worth a couple of hours.
http://www.journeymuseum.org/visit Take Exit 58 off of I-90 and go south to New York St, turn left, you are there.
Another museum I did not visit, but looks promising for next time is the High Plains Western Heritage Center at Spearfish.
http://www.westernheritagecenter.com/
Do not miss Devils Tower. The Wyoming Welcome Station at exit 199 in Wyoming is worth the visit on the way to Devils Tower, as it has nice displays, not just racks of brochures. I was impressed by the quality. Vore Buffalo Jump is just up the frontage road a mile and worth the tour.
On the south end of the Black Hills is Hotsprings, and the Mammoth Site, also well worth the visit.
Rushmore is good for about two hours of your time, free admission, $10 parking unless over age 62, then $5. I spent more time at Crazy Horse, $11 admission, lots of Native American stuff in the Museum.
My whirlwind tour of the Badlands and Black Hills and eclipse....
http://www.rvforum.net/SMF_forum/index.php/topic,110023.0.html
Charles
2007 Winnebago View 523H on a 2006 Dodge (Daimler-Chrysler aka Mercedes) Sprinter 3500 chassis (T1N). Bought Sept 2015 with 18K miles on it, Prog Ind HW30C, Prog Dymanics PD4645, Coleman Chill Grille, PML/Yourcovers.com deep alum trans pan, AutoMeter 8558 trans temp gauge, Roadmaster sway bar, Koni Red shocks (front & rear), Fantastic Ultra Breeze hood, added OEM parabolic mirrors and RH aspherical mirror, MB grill conversion.