This is one of six Renville County Parks that offers camping. All camping here is rustic, no hookups/dump/fill. I didn't see any mentions in the park of fees to get in the park, to use the park, or to camp there. But the county's fee schedule indicates $15/night: http://www.renvillecountymn.com/ParksandRec/2017%20Park%20Fee%20Schedule.pdf - no clue how one would go about paying.

The campground didn't seem too organized, possibly two or three official spots, possibly a go-wherever-you-want situation. They apparently have toilets and water, but I didn't see them. The camping spots were mostly wooded, and near the river. Here are coordinates to the camping loop: (44.730280, -95.405977).

The camping spots are not RV friendly due to the small size. But, I don't get the feeling too many people come here, so I can't imagine an RVer parking at the main entrance area would get hassled overnight. There's also a wayside rest (44.734256, -95.409807) and a historical site that has a big parking area (44.731650, -95.408264).

If you're looking for hookups, Upper Sioux Agency State Park is just down the road.