Yellow River Forest is spectacular this time of year.
If someone's really looking for a wilderness-esque experience in Iowa, I would strongly recommend a fall visit to White Pine Hollow. It's right outside of Luxemburg (between Dubuque and Guttenberg). It's a massive chunk of publicly owned land with very few actual trails. You're basically bushwacking, but once the leaves turn and start to fall, it's easily to keep your bearings. A beautiful stream with it's cliffy canyon flows through it.
You could base a great Driftless Area weekend out of Decorah, McGregor, Dubuque, or Elkader. Just depending on what places you want to check out.
One thing I'd recommend as well for someone looking for uncrowded scenery, is to hike along a designated trout stream. There will be public access, some level of trail, and you'll get into some beautiful spots.
