The campground is across the creek (Musselshell River) from the fairgrounds with an old bridge connecting them. The park is a bit east of downtown Roundup, not south as shown on the map here. Just look for the signs for the fairgrounds when you get into Roundup. We were the only ones in the campground when we arrived at 2:30 pm. By 6:30 pm there were four other campers there. It is a quiet nice place with lots of shade trees. No electric but there was one water spigot near the restrooms. We made a small contribution in the donation box at the front of the park. There is a wilderness path that is explained on the bulletin board at the entrance to the park. We did that walk in one hour. A lot of it is along the creek. Some families came in the afternoon and let their kids play in the creek below the bridge. We will go back if in that area of Montana again.
Donation only park. No electric, two sites with water. Did have a bathroom. We parked on the grass. Had a fire ring. Very quiet.