St Mary'S Lake
St. Louis County, Minnesota234 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for St Mary'S Lake. Here is what has been measured.
- Impaired · Mercury
- 44 ft max depth
- Limited data
St Mary'S Lake in St. Louis County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 15 ft visibility. Maximum depth: 44 ft. Surface area: 234.16 acres.
Minnesota DNR's Standard Survey on July 21, 2025 caught 1.17 walleye per gill net at St Mary'S Lake. DNR survey details →
St Mary'S Lake is a 234-acre lake in St. Louis County, Minnesota with a maximum depth of 44 feet. Overall water quality is declining over recent sampling years. The lake supports 14 documented fish species including black crappie, bluegill, and brown bullhead. No public access — the lake is private or restricted.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-08-14. Methodology: how these readings are compared.
What St Mary'S Lake is good for
From access and monitoring records, not editorial picks.
- Clear water15 ft of visibility
- Fishing14 species recorded
- Ice seasonIce-out around Apr 24
- Deep water44 ft surveyed max depth
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. St Mary'S Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Whether St Mary'S 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 St Mary'S Lake
These are the measurements Minnesota PCA publishes for St Mary'S Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Crystal clear, you can see 15 ft down. TSI 38.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 15ft | 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. | 38 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about St Mary'S Lake
Answers come straight from the public measurements and survey records on this page.
Minnesota DNR's Standard Survey on July 21, 2025 caught 1.17 walleye per gill net at St Mary'S Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows St Mary'S Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
6 surveys on file from MN DNR Fisheries. Most recent: 2025-07-21 (Standard Survey).
6 surveys on file · most recent 2025-07-21 (Standard Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Bluegill | 26.00 | 3–7 in 2025-07-21 | 0.12 lb |
| Largemouth Bass | 9.80 | 4–16 in 2025-07-21 | 0.76 lb |
| Pumpkinseed | 9.71 | 3–7 in 2025-07-21 | 0.19 lb |
| Green Sunfish | 5.67 | 3–5 in 2011-08-08 | 0.15 lb |
| Fathead Minnow | 5.40 |
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.
Bluegill
Largemouth Bass
Pumpkinseed
Green Sunfish
From the 2025-07-21 survey
St. Mary's is a 234-acre lake located 2 miles south of Eveleth off the Miller Trunk Road. It shares much in common with Armstrong, Bass (Biwabik), and Ely lakes in the Tower Area. The water is clear, Secchi visibility is 13 feet, and the lake is up to 44 feet deep. St. Mary's was thermally stratified on 07/21, with a…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for St Mary'S Lake. 3 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — St. Mary'sFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — St. Mary's (1772)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — St. Mary'sFish Stocking History · MN DNR LakeFinder
Lake Details
Max depth
44 ft
Surface area
234 acres
Shoreline
4.1 mi
Littoral zone
33%
Share shallower than 15 ft
Public access
No
Listed by Minnesota PCA
Stays via Stay22
Stays near St Mary'S Lake
Compare lakeside cabins, hotels, and vacation rentals near St Mary'S 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 St Mary'S 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 St Mary'S 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 St Mary'S Lake
Water Quality Trend: Worsening
Based on 6 years of monitoring (2020–2025).
Water clarity
Worsening6 years
Ice season
Typical ice-out
Apr 24
Earliest Apr 9, 2017 · Latest May 5, 2023
Typical ice-in
Nov 22
Earliest Nov 18, 2018 · Latest Nov 29, 2015
Most recent ice-out
May 5
2023
17 observations · Minnesota PCA ice records
EPA Impairment Status
St Mary'S 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 MN69-0651-00 · Official waterbody report
Regulated Pollution Sources Nearby
2 EPA-permitted facilities operate within about 5 miles of St Mary'S Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Eveleth WwtpEveleth · 2.4 mi away · NPDES MN0023337Recent violation
- Eveleth Mines Llc Dba EvtacEveleth · 1.6 mi away · NPDES MN0044946
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
Nearby Lakes in St. Louis County
Frequently asked questions about St Mary'S Lake
Where is St Mary'S Lake?
- St Mary'S 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 St Mary'S Lake?
- St Mary'S Lake in St. Louis County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 15 ft visibility. Maximum depth: 44 ft. Surface area: 234.16 acres.
Is St Mary'S Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. St Mary'S Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
How deep is St Mary'S Lake?
- St Mary'S Lake has a maximum depth of 44 feet. The lake covers 234.16 acres.
What fish are in St Mary'S Lake?
- Fish species found in St Mary'S Lake include black crappie, bluegill, brown bullhead, cisco species, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, rock bass, tullibee (cisco), walleye, white sucker, yellow bullhead, yellow perch. St Mary'S Lake is located in St. Louis County, Minnesota.
What did the DNR fisheries survey find at St Mary'S Lake?
- Minnesota DNR's Standard Survey on July 21, 2025 caught 1.17 walleye per gill net at St Mary'S Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows St Mary'S Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
When does St Mary'S Lake thaw?
- St Mary'S Lake typically has ice-out around Apr 24. Ice typically forms around Nov 22. The open water season is approximately 212 days.
Can I fish at St Mary'S Lake?
- Public access to St Mary'S 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 St Mary'S Lake across LakeQuality
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
Oligotrophic Lakes in Minnesota
Where this data comes from
14 measurements from 1 monitoring station, 2020–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA14 samples · 2020–2024
Analytical methods
- Field measurement/observation, generic method
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
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake details from Minnesota DNR LakeFinder
Ice data from Minnesota DNR Climate