O'Leary Lake
O'Leary Lake in St. Louis County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 10.7 ft visibility. Maximum depth: 52 ft. Surface area: 202.17 acres.
- Clarity
- 10.7 ft
- Max depth
- 52 ft
- Area
- 202 acres
- Public access
- No
Next lake in St. Louis County
Why O'Leary Lake has no grade
We grade a lake only when its monitoring record clears the evidence bar: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For O'Leary Lake, the only measurement available is water clarity, which is not a water-quality indicator on its own — EPA's National Lakes Assessment does not grade clarity. Sampling here has recorded water clarity, but not phosphorus and algae (chlorophyll-a).
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by MPCA and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
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. Grade methodology: LakeGrade methodology.
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Swimming Safety
Not ratedLimited data
Not rated for swimming — there is not enough monitoring data to judge this lake
Water quality measurements for O'Leary Lake
These readings exist but do not meet the evidence bar for an A–F grade — see why.
Good clarity, visible to about 10.7 ft. Trophic State Index: 43.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 10.7 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 43 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay 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
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Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 52 ft |
| Average Depth | 25 ft |
| Surface Area | 202 acres |
| Shoreline Length | 2.5 mi |
| Littoral Zone | 32% |
| Public Access | No |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Fish Species
Click a species to see every graded lake where it is documented.
Fishing O'Leary Lake
DNR Fisheries Survey Summary
2 surveys on file from MN DNR Fisheries. Most recent: 2016-08-22 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Pumpkinseed | 7.28 | 0.04 lb |
| Northern Pike | 3.71 | 2.62 lb |
| Yellow Perch | 3.65 | 0.08 lb |
| TPM | 2.33 | — |
| Smallmouth Bass | 2.21 | 1.85 lb |
| GOS | 1.67 | — |
CPUE = catch per unit effort, averaged across surveys (excludes juvenile shoreline seining). Higher CPUE = more abundant in standardized sampling.
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
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
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN69-0685-00 · Official waterbody report
Graded lakes near O'Leary Lake
O'Leary Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in St. Louis County
Frequently asked questions about O'Leary Lake
What is the water quality grade for O'Leary Lake?
- O'Leary Lake in St. Louis County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 10.7 ft visibility. Maximum depth: 52 ft. Surface area: 202.17 acres.
Is O'Leary Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. O'Leary Lake is not rated for water quality — its monitoring record does not meet the evidence bar. Always check local health department advisories before swimming.
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.
Explore O'Leary Lake across LakeGrade
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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)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated 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