If all the numbered sites are taken, they have an overflow area without hookups. We were here on a late June Saturday and it was full, except for the overflow.
This is a similar spot to other areas located around the reservoir in that it is wide open giving you that fantastic Montana Big Sky feeling. During the week there's hardly anyone up here so there's a good chance you won't have any neighbors. Each site has a fire ring and picnic table. There are also vault toilets nearby and a fish cleaning station!
This us a great campground. It's close to the water and other recreational areas. The kids ponds are great for young fishers.
There are several free campgrounds around the Fort Peck area. We stayed at West End which has three loops, toilets, fire rings and picnic tables. Dogs are welcome. Great views for sunrise/sunset here. It did get a little windy on the lake shore but other than that it was a nice quite spot. Several RVs there with boats if you can about that kind of noise.