Armstrong Lake
St. Louis County, Minnesota382 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Armstrong Lake. Here is what has been measured.
- Impaired · Mercury
- 34 ft max depth
- Public access
- Limited data
Armstrong Lake in St. Louis County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 16.2 ft visibility. Maximum depth: 34 ft. Surface area: 382.34 acres.
Minnesota DNR's Standard Survey on August 9, 2021 caught 4.44 walleye per gill net at Armstrong Lake. Length samples in the latest survey that recorded them ran 10–26 inches. DNR survey details →
Armstrong Lake is a 382-acre lake in St. Louis County, Minnesota with a maximum depth of 34 feet. Overall water quality is declining over recent sampling years. The lake supports 10 documented fish species including black crappie, bluegill, and largemouth bass. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2023-09-03. Methodology: how these readings are compared.
Armstrong Lake covers about 380 acres in St. Louis County. It has one public boat landing. The median ice-out date is March 31, which is when the open-water season begins. For a place on the water, look through cabin and lake-house rentals near Armstrong Lake on Vrbo. For a hotel or motel room, Booking.com and Expedia both search around the lake.
What Armstrong Lake is good for
From access and monitoring records, not editorial picks.
- Clear water16.2 ft of visibility
- Boat launch1 documented ramp
- Fishing10 species recorded
- Ice seasonIce-out around Mar 31
- Deep water34 ft surveyed max depth
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Armstrong Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Whether Armstrong 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 Armstrong Lake
These are the measurements Minnesota PCA publishes for Armstrong 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 16.2 ft down. TSI 37.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 16.2ft | 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. | 37 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Armstrong Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Armstrong Lake typically sits around 66°F at the surface in September. Summer average is about 65°F. Usually warmest in Aug (about 69°F) and coldest in May (about 55°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (55°F) to its warmest (69°F).
Typical surface water temperature by month, from 31 field readings (2016–2016) via the EPA Water Quality Portal. See the full Armstrong Lake water temperature breakdown →
Minnesota DNR's Standard Survey on August 9, 2021 caught 4.44 walleye per gill net at Armstrong Lake. Length samples in the latest survey that recorded them ran 10–26 inches.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Armstrong Lake’s water-quality measurements separately, and the water-quality trend over 5 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
8 surveys on file from MN DNR Fisheries. Most recent: 2021-08-09 (Standard Survey).
8 surveys on file · most recent 2021-08-09 (Standard Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Bluegill | 24.60 | 3–8 in 2021-08-09 | 0.17 lb |
| Largemouth Bass | 11.73 | 4–17 in 2021-08-09 | 0.74 lb |
| Walleye | 3.43 | 10–26 in 2021-08-09 | 3.21 lb |
| White Sucker | 3.34 | 16–20 in 2021-08-09 | 2.27 lb |
| Northern Pike | 3.15 | 16–34 in 2021-08-09 | 2.32 lb |
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
Walleye
White Sucker
From the 2021-08-09 survey
Armstrong Lake is a 382 acre lake located 10 miles west of Ely. It is accessed by a concrete ramp off Hwy 169. The lake has a maximum depth of 34 feet and clear water at the time of this survey. On August 9, 2021 the lake was thermally stratified with a surface temperature of 72 F and a bottom temperature of 54 F.…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Armstrong Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — ArmstrongFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Armstrong (1864)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — ArmstrongFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — ArmstrongPublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
34 ft
Surface area
382 acres
Shoreline
4.5 mi
Littoral zone
27%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
6 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,450 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Armstrong LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Armstrong Lake
Compare lakeside cabins, hotels, and vacation rentals near Armstrong 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 Armstrong 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 →
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Fish Species
Click a species to see every lake where it is documented.
Fishing Armstrong Lake
Water Quality Trend: Worsening
Based on 5 years of monitoring (2020–2024).
Water clarity
Worsening5 years
Ice season
Typical ice-out
Mar 31
Earliest Mar 31, 2010 · Latest May 14, 2015
Most recent ice-out
May 14
2015
3 observations · Minnesota PCA ice records
EPA Impairment Status
Armstrong 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 MN69-0278-00 · Official waterbody report
Nearby Lakes in St. Louis County
Frequently asked questions about Armstrong Lake
Where is Armstrong Lake?
- Armstrong 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 Armstrong Lake?
- Armstrong Lake in St. Louis County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 16.2 ft visibility. Maximum depth: 34 ft. Surface area: 382.34 acres.
Is Armstrong Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Armstrong Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
What is the water temperature of Armstrong Lake?
- Armstrong Lake typically sits around 66°F at the surface in September, from 31 EPA Water Quality Portal field readings (2016–2016). That is a typical value for the month, not a live reading.
How deep is Armstrong Lake?
- Armstrong Lake has a maximum depth of 34 feet. The lake covers 382.34 acres.
What fish are in Armstrong Lake?
- Fish species found in Armstrong Lake include black crappie, bluegill, largemouth bass, northern pike, pumpkinseed, rock bass, smallmouth bass, walleye, white sucker, yellow perch. Armstrong Lake is located in St. Louis County, Minnesota.
What did the DNR fisheries survey find at Armstrong Lake?
- Minnesota DNR's Standard Survey on August 9, 2021 caught 4.44 walleye per gill net at Armstrong Lake. Length samples in the latest survey that recorded them ran 10–26 inches. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Armstrong Lake’s water-quality measurements separately, and the water-quality trend over 5 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
When does Armstrong Lake thaw?
- Armstrong Lake typically has ice-out around Mar 31.
Are there boat ramps on Armstrong Lake?
- Armstrong Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Armstrong Lake. Public access is listed as yes.
Can I fish at Armstrong Lake?
- Armstrong Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. 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 Armstrong 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
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Where to stay at Minnesota's top lakes, each with its readings
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Where this data comes from
72 measurements from 4 monitoring stations, 2020–2023. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA72 samples · 2020–2023
Analytical methods
- Field measurement/observation, generic method
Monitoring station identifiers (4)
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
Named boat-access points from the USGS National Boat Ramps inventory
Ice data from Minnesota DNR Climate