There is a state park around this lake plus at least three COE campgrounds where you get a discount for being one of those seniors. I made a reservation for an electric site at Boulder Marina Campground because I was told it was quieter than the others. Reservations are recommended, especially on the weekend because there are a lot of boaters and fishers here.
It is about 15 miles south of I 70, about 60 miles east of St. Louis, MO, so it is really on the way to a lot of things.
The electric/water area ($8) is older and more shaded, but I preferred the newer full hookup area ($12) because I wanted to use my satellite TV. I ended up moving to Site 7, which was huge and spotless. There are only about 10 full hoohup sites, by the way. Here is the link to the COE site: http://www.mvs.usace.army.mil/Missions/Recreation/CarlyleLake/Maps.aspx
Here is a photo of the older area:
Here are some photos of the newer area. This is an incredible site, especially for the price. There was an even bigger pull-through site right next door but I have no photos:
The new area is very close to the marina:
This last is of the lake itself.