William O'Brien State Park
William O'Brien State Park is a state park in Washington County. It was established in 1947. 8 lakes with water-quality readings 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 measured lakes are within easy reach of the park. Square Lake has the lowest nutrient and algae readings 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 readings for that lake give you the clarity, nutrient, and algal-pressure context you need.
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Official Resources
Nearby Lakes (within 15 mi)
Lakes closest to William O'Brien State Park, weighted by size. Click a lake for its water-quality readings, fish species, and depth.
| Lake | County | Surface Area | Distance |
|---|---|---|---|
| Long Lake | Washington | 1,799 acres | 3.2 mi |
| Sand Lake | Washington | 47 acres | 2 mi |
| Square Lake | Washington | 203 acres | 4.7 mi |
| Goose Lake | Washington | 76 acres | 4 mi |
| Hay Lake | Washington | - | 2.5 mi |
| Big Carnelian Lake | Washington | 457 acres | 6.2 mi |
| Big Carnelian Lake | Washington | 457 acres | 6.4 mi |
| Forest Lake | Washington | 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
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Source: EPA National Aquatic Resource Surveys, 2026.