We stopped in the Black Hills on the way home from Yellowstone/Grand Teton in 2020. We only had 2 nights and 1 day scheduled there, but we enjoyed it so much that we went back in 2021 for a week. Plan to go back this summer too. We've biked on the Mickelson trail, and did a bunch of hikes in the Black Elk Wilderness (have climbed Black Elk Peak twice - once on the regular route from Sylvan Lake and another route where you come in from the north. It's much longer, twice the elevation, and you have the trail to yourself).
From north Iowa, it's only a 7-8 hour drive and you're in legitimate mountain terrain. It's such an easy drive, reasonably priced, and you get a very Midwestern vibe yet. I love it.