I grew up in nearby Bloomington, Indiana, and my family were actually the very first campers at Hardin Ridge in 1966. We unwittingly set up camp the weekend before the campground opened, and we saw a picture of our travel trailer on the front page of the Bloomington Herald-Telephone with a caption "Somebody jumped the gun at the new Hardin Ridge Campground!"
This is a great place to set up camp for a week or two. In summer there is a nice sandy beach on the shore of Lake Monroe (it was free last time I went) with a simple shower house. The six camping loops have several vault toilets, and most have shower houses with flush toilets. While the campgrounds are fully open April 15 to October 15, you can camp year round if you are set up to dry camp. The very first camp loop (Holland Ridge) is often open all year, and no fees are charged when the water is off.
This campground was the destination for many a summer camping trip when I was a child, and for many more when my own kids were little. It's also not far from the Hoosier National Forest, with a horsemen's camp and trails, and a little further east a dozen or so dispersed camp sites.