Below the bluffs at St. Croix Bluffs Regional Park, wooded ravines cut down through upland prairie to the St. Croix. The Washington County park holds 685 acres and 3,800 feet of shoreline, room enough for a family to scatter by day: the kids down in the ravines, someone walking the prairie up top, someone else just watching the river. Twin Cities families come back to it weekend after weekend, and the ones who stretch a weekend into a week rarely find a reason to move the rig once it's level.
Anyone bringing a boat gets a launch with parking for 50 trailers, and the river fills the days from there. Evenings belong to the campground, with chairs out on the pad, dinner outside, and the St. Croix going dark below the bluffs.
The campground is laid out for staying put. Washington County's camping page lists 26 pull-through sites with water and 20, 30 and 50 amp electric, along with 36 back-in sites on 20 or 30 amp. There's a trailer and RV dump station in the park, plus a bathroom with showers. A family can run the air through a muggy July week and empty the holding tanks without ever breaking camp.
Book the pull-through first and the motorhome second. Those water and 50 amp sites are what make a full week comfortable in a big rig, and summer weekends claim them early. Washington County runs Lake Elmo Park Reserve on the same reservation system, which makes it the easy fallback when the Bluffs is full.
Late summer brings the Minnesota State Fair, when the fairground campground in the middle of the city fills with rigs for the run of the fair. Fair weeks draw on the same rentals and the same metro campsites as a late-summer week on the river, so a family planning the St. Croix around fair time should lock in the site early and the rig right after.
Wild River State Park, farther up the St. Croix
North of the metro, Wild River State Park follows 18 miles of the St. Croix through paddling and horseback country, with interpretive programs and, once the snow falls, ski and snowshoe trails. It works as a long day out from the Bluffs, but it's better as the second half of the week. A few nights on the county pad with power, then the move upriver for days on the water and on the horse trails.
Reserve the Wild River campsite with Minnesota DNR before settling on the rig, the same order as at the Bluffs, and read that site's details there before you match a motorhome to it. Emptying the tanks at the Bluffs dump station on the way out keeps the move north simple.
William O'Brien and Interstate State Park at the Dalles sit on the same river, and they're written up with Lake Elmo and the State Fair campground on the Saint Paul campervan page, the better fit when it's two people instead of a family. Minneapolis's Three Rivers parks are on the Minneapolis campervan page, and the Minnesota RV page picks up the North Shore and the Brainerd lakes for a rig.