O'Leary Lake
St. Louis County, Minnesota202 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for O'Leary Lake. Here is what has been measured.
- Impaired · Mercury
- 52 ft max depth
- Limited data
O'Leary Lake in St. Louis County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 10.7 ft visibility. Maximum depth: 52 ft. Surface area: 202.17 acres.
Minnesota DNR's Standard Survey on August 22, 2016 caught 3.33 walleye per gill net at O'Leary Lake. DNR survey details →
O'Leary Lake is a 202-acre lake in St. Louis County, Minnesota with a maximum depth of 52 feet (25-foot average). The lake supports 9 documented fish species including black bullhead, bluegill, and largemouth bass. No public access — the lake is private or restricted.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2023-08-01. Methodology: how these readings are compared.
What O'Leary Lake is good for
From access and monitoring records, not editorial picks.
- Clear water10.7 ft of visibility
- Fishing9 species recorded
- Deep water52 ft surveyed max depth
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. O'Leary Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Whether O'Leary Lake is safe to swim in today is a call for the Minnesota Pollution Control Agency and the Minnesota DNR and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for O'Leary Lake
These are the measurements Minnesota PCA publishes for O'Leary Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Good clarity, visible to about 10.7 ft. TSI 43.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 10.7ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | No reading The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. | |
| Chlorophyll-a (algae) | No reading The green pigment in algae — a direct measure of how much algae is in the water. | |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 43 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about O'Leary Lake
Answers come straight from the public measurements and survey records on this page.
Minnesota DNR's Standard Survey on August 22, 2016 caught 3.33 walleye per gill net at O'Leary Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows O'Leary Lake’s water-quality measurements separately. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
2 surveys on file from MN DNR Fisheries. Most recent: 2016-08-22 (Standard Survey).
2 surveys on file · most recent 2016-08-22 (Standard Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Pumpkinseed | 7.28 | 3 in 2016-08-22 | 0.04 lb |
| Northern Pike | 3.71 | 20–26 in 2016-08-22 | 2.62 lb |
| Yellow Perch | 3.65 | 3–6 in 2016-08-22 | 0.08 lb |
| Smallmouth Bass | 2.21 | 5–19 in 2016-08-22 | 1.85 lb |
| Golden Shiner | 1.67 |
CPUE = catch per unit effort, fish caught per net per set in a standardised survey. It measures abundance, not size, and is not a weekly bite report.
Length Distributions
Number of fish caught at each inch class in the most recent survey that recorded lengths. Red dashed line marks an approximate trophy threshold for that species.
Pumpkinseed
Northern Pike
Yellow Perch
Smallmouth Bass
From the 2016-08-22 survey
O'Leary Lake is a 202 acre class 5 lake located in Voyageurs National Park. This interior park lake is located approximately 10 miles north-northwest of the community of Crane Lake, Minnesota. O'Leary is accessed via a portage trail from Hammer Bay in the east end of Namakan Lake, and no boats are allowed to be…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for O'Leary Lake. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — O'LearyFisheries Lake Survey · MN DNR LakeFinder
Lake Details
Max depth
52 ft
Average depth
25 ft
Surface area
202 acres
Shoreline
2.5 mi
Littoral zone
32%
Share shallower than 15 ft
Public access
No
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
1 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,129 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Stays via Stay22
Stays near O'Leary Lake
Compare lakeside cabins, hotels, and vacation rentals near O'Leary Lake in St. Louis County, Minnesota — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
Top-rated places to stay near O'Leary Lake
Prices for Oct 9–11, 4 adults. Change dates on the map below.
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 whole trip? See where to stay at Minnesota’s top lakes →
Follow O'Leary Lake’s readings
Email me when new measurements post for this lake. Updates stay free.
Or email
Fish Species
Click a species to see every lake where it is documented.
Fishing O'Leary Lake
EPA Impairment Status
O'Leary Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
Designated uses not supporting: Fish consumption.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN69-0685-00 · Official waterbody report
Nearby Lakes in St. Louis County
Frequently asked questions about O'Leary Lake
Where is O'Leary Lake?
- O'Leary Lake is a lake in St. Louis County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of O'Leary Lake?
- O'Leary Lake in St. Louis County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 10.7 ft visibility. Maximum depth: 52 ft. Surface area: 202.17 acres.
Is O'Leary Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. O'Leary Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
How deep is O'Leary Lake?
- O'Leary Lake has a maximum depth of 52 feet and an average depth of 25 feet. The lake covers 202.17 acres.
What fish are in O'Leary Lake?
- Fish species found in O'Leary Lake include black bullhead, bluegill, largemouth bass, northern pike, pumpkinseed, smallmouth bass, walleye, white sucker, yellow perch. O'Leary Lake is located in St. Louis County, Minnesota.
What did the DNR fisheries survey find at O'Leary Lake?
- Minnesota DNR's Standard Survey on August 22, 2016 caught 3.33 walleye per gill net at O'Leary Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows O'Leary Lake’s water-quality measurements separately. Catch rate is not a swim clearance and is not a weekly bite report.
Can I fish at O'Leary Lake?
- Public access to O'Leary Lake is listed as no on the lake record, so confirm before you make the trip. Seasons, size and bag limits, and whether you need a license are set by Minnesota's fish and wildlife agency, so check its current regulations before you go.
Explore O'Leary Lake across LakeQuality
Depth, room, public access, and the state wake-sport rules
Fish species and the cleanest lakes across Minnesota
Fish species and best lakes in St. Louis County
Species activity outlook by water temperature and season
Top lakes and where to stay in the Lake Vermilion Area area
Where to stay at Minnesota's top lakes, each with its readings
Lakes in the Lake Superior Basin (MN+WI), ranked by water quality
Lakes in the Rainy Lake Watershed, ranked by water quality
Minnesota's cleanest lakes, ranked on agency measurements
More lakes in Minnesota
Other Lakes in Minnesota
Mesotrophic Lakes in Minnesota
Where this data comes from
3 measurements from 1 monitoring station, 2023. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- USGS Minnesota Water Science Center
USGS-MN3 samples · 2023
Monitoring station identifiers (1)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder