Near the town of Three Forks, to which there are both short/scenic bike trails and an 18-miler. 6 of the 17 tent sites are 1st-come, 1st-serve. With a ton of historical displays, friendly park rangers, an open-air, welcoming vibe and a sprawling variety of other things to explore, staying here will put a smile on your face.  There's decent distance between some of the sites, but some of them aren't very large.