This appears to be a Hiawatha National Forest campground. Though short by UP standards it appears from the map and the types of roads that it's about an hour to Munising. I've stayed at Wandering Wheels just outside of Munising and it is a very nice campground (privately owned). I haven't seen too many NF camp sites that would RV friendly. Were they the typical small sites or did you happen to find a larger one? Pictures?