William O'Brien State Park
William O'Brien State Park is a state park in Washington County. It was established in 1947. 8 graded lakes are within 15 miles of the park, including Long Lake, Sand Lake, Square Lake.
William O'Brien State Park is a Minnesota State Park covering an unrecorded acreage acres. State parks are the most heavily-developed of the public-land designations — campground, picnic, boat-launch, interpretive-center. 8 graded lakes are within easy reach of the park, with an average grade of C. Square Lake (A) is the cleanest of the set.
For visitors planning around water quality, the nearby-lakes list below is the practical tool: a park is only as good as the lake you intend to use it from, and the LakeGrade for that lake gives you the water-clarity, nutrient, and algal-pressure context you need.
Official Resources
Nearby Graded Lakes (within 15 mi)
Lakes closest to William O'Brien State Park, weighted by size. Click a lake for its full water quality grade, fish species, and depth.
| Lake | County | Grade | Surface Area | Distance |
|---|---|---|---|---|
| Long Lake | Washington | D | 1,799 acres | 3.2 mi |
| Sand Lake | Washington | D | 47 acres | 2 mi |
| Square Lake | Washington | A | 203 acres | 4.7 mi |
| Goose Lake | Washington | D | 76 acres | 4 mi |
| Hay Lake | Washington | C | - | 2.5 mi |
| Big Carnelian Lake | Washington | A | 457 acres | 6.2 mi |
| Big Carnelian Lake | Washington | A | 457 acres | 6.4 mi |
| Forest Lake | Washington | C | 2,271 acres | 9.3 mi |
Other Parks in the Area
- Interstate Park— State Park, 12.9 mi
- Interstate State Park— State Park, 13 mi
- Wild River State Park— State Park, 20 mi
- Afton State Park— State Park, 24.7 mi
Where to stay near William O'Brien State Park
Compare cabins, hotels, and vacation rentals near William O'Brien State Park — find a place to stay close to the park and its nearby lakes.
Top-rated places to stay near William O'Brien State Park
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a trip to William O'Brien State Park?
Get lake water-quality report cards plus the best cabin & lodging deals near William O'Brien State Park — straight to your inbox. No spam, unsubscribe anytime.
Source: EPA National Aquatic Resource Surveys, 2026.