We were just passing through the area south of Dubuque and stayed here on a rainy night. Camping is in the Dyas unit, but there are a few trails and a butterfly garden in the Nelson unit (down the road) but no camping. The butterfly garden was suffering a bit from neglect in August.
It was a decent place to stay for a night, but sites were kinda tight, i.e. close to each other. It's still a bargain at $11/$16 for non-electric/electric sites from 5/1-9/30, and the cost is $6/$11 the rest of the year.
The standard amenities include:
fire ring and picnic table at each site
dump station and potable water
modern bathrooms (as well as pit toilets near the road to sites 11-23…not sure why you'd use these because it's not much farther to a real bathroom)
individual showers, i.e. a door to the outside at each shower
Be sure to check out the photo that shows the site map along with a video that shows each area on that map.
We camped at Bellevue last summer (Aug. 2017) & it was not at all crowded. It was a really nice campground with new shower & bathroom facilities. We had stayed there because we couldn't get a site at Maquoketa Caves State Park and ended up quite happy.