| Portsmouth Mine Pit Lake | |
|---|---|
| A view of the swimming area from the campground on the west shore of the lake. | |
| Location | Crosby, Minnesota |
| Lake type | artificial lake |
| Basin countries | United States |
| Surface area | 121 acres (49 ha) |
| Max. depth | 450 ft (140 m) |
Portsmouth Mine Pit Lake, sometimes called the Portsmouth Pit, is the deepest lake in Minnesota at over 450 feet (137 m), according to the most recent Minnesota DNR data. The 120-acre (49 ha) artificial lake is a former iron mining pit in the Cuyuna Range that has since filled with water.
The Portsmouth Mine Pit is part of the Cuyuna Country State Recreation Area, located in Crow Wing County. The lake is within Crosby-Ironton city limits.
In the last five years, the Minnesota DNR has repeatedly stocked the lake with brook and rainbow trout.
On August 19, 1957, the mine pit, then not yet filled with water, served as launch site for a big stratospheric balloon; the second flight of the Air Force's Project Manhigh.