Wind Cave is really something. That elevator ride down tho... eek. I enjoyed the lands around the caves more than the cave itself. Make sure to check out the Journey Museum in Rapid City if you want to get a great idea of the native experience during that time. It is quite shameful. I didn't feel very proud visiting Mt Rushmore and visiting Crazy Horse felt odd too, knowing that Crazy Horse memorial is basically a non-native money-making scam. The real eye opener was visiting the Wounded Knee massacre site in the southern portion of the badlands on the Oglala Souix / Badlands NP co-op. It really was like transporting back in time, but in a sad, unneeded way. On a positive note, the ranger station on the White River staffed by native american rangers was one of my all time favorite visitor center stops. Take the rock tour. Our kids get the junior ranger badges and have quite the collection.
My most memorable National Monument visit was to Katahdin Woods & Waters in Maine, adjacent to Baxter State park. We visited shortly after it opened and the park was very new & raw. There were no maps, no visitor center, and the overlooks had crude wooden signs labelled basic names like "Overlook 1". We went there to stargaze under Bortle 1 skies watching the Perseids blast off. I've never been under stars like that, and I've been to some incredible dark sites in both the US and Canada. We stayed at "Overlook 2" until 1am and then drove the 20 miles out on a gravel, winding road. We didn't arrive home until around 3am. We also encountered a bull moose on the road on our way out. That was intense.
On the way in/out of the park, the road was filled with "NATIONAL PARK NO" and "NATIONAL PARK YES" signs, apparently indicating what side of the fence each local was on. At one river crossing, we spoke with a fisherman and he told us that he was glad about the park. He didn't want to see the land logged again, and that was a big reason why the monument was created. The woods were apparently logged every 30 years or so and that time was coming up again. All of this discourse reminded us of what we read while at Acadia National Park, where intreprative signs detailed the local battles between the residents, the Rockefellers, and the government. There were even old pictures of signs that either protested or supported the park. Some things never change
Another cool thing about this park is it hosts the western terminus of the International Appalachian Trail (IAT), that crosses the pond and extends all the way down to Morocco. The mountain range used to be contigiuous back during the Pangea days.
Highly recommended to check this out if you ever have the opportunity. I've been to many out of the way places. We've spent a ton of time in Canada as well. I've been to many of their provincial and national parks. The USA is still top tog in that regard... it is hard to match the look and feel of a USA National Park