William O'Brien State Park has two different camp grounds (plus a couple of group camp grounds and two hike-/cart-in sites. We stayed at the Riverview campground. down the river bluffs from the main portion of the park, and as the name implies, on the shores of the St. Croix River. Our site was a non-electric site on the outside ring, with just a thin slip of woods and a hiking trail between us and the St. Croix river. On a hot summer day, the breeze off the river would be welcoming and cooling, but on an abnoramlly chilly spring day, the wind off the river was a bone-chilling constant. The campsite itself was situated about 500' from the shower/bathroom, and those facilities were clean, and in service, but otherwise unremarkable. There was not a lot of other tent campers at the campground, likely the cold temps kept some folks away, but the electric sites in the rest of the campground were filled with campers. We had the unfortunate experience of being across the road from the loudest group of campers in the campground, as a part of eight different families and their campers used the site across the road from us as their main gathering point. Quiet hours at the campground are from 10pm to 8am, and their festivities carried on until nearly 2am both nights. There was no effort from park staff to enforce quiet hours, which was a bummer.
With the exception of the loud neighbors, and unseasonable cold weather, this was a solid campground, and being near the river with quick access to the hiking trail was a plus.