One of my favorite locations to camp in Iowa as a Boy Scout growing up was Ledges State Park. Since I hadn't been back in years, I decided to check it out and spend a night camping there. It's close to how I remember it.
The campground has a good picnic area, restrooms, and an excellent trail. It's also inexpensive.
What I enjoy most about this park compared to others in Iowa are the sandstone ledges and the slopes on the trail. There are some excellent views, so make sure your phone has enough battery to take photos (unlike me). I also spent a lot of time off the trail. It isn't too hard to get around. I'm not one who enjoys staying at a park that is mostly flat, so this is definitely a good place in Iowa for me to camp.
If you are looking for a cool place to camp within an hour of Des Moines, you should seriously consider this park.