We spent the night at Deerwood Park Campground, just off I-380 in Evansdale, IA.
Deerwood Park is a large, clean, seasonal campground with a good offering over overnight spots - no reservations. There's also a Walmart right across the river in Waterloo if you need to do some shopping.
All the sites at Deerwood Park are back-in and include water and electric for $15/night. Each site has a fire pit and a picnic table. The park also has a dump station. Pay at the kiosk (cash or check) in the center of the campground.
If you're passing through the area and need a nice place to stay, you won't go wrong here.
Today we're heading to Sioux Falls, SD, where we'll spend a couple nights.