Alton Lake
Cook County, Minnesota969 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Alton Lake. Here is what has been measured.
- Impaired · Mercury
- 72 ft max depth
- Limited data
Alton Lake in Cook County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 13.5 ft visibility. Maximum depth: 72 ft. Surface area: 968.63 acres.
Minnesota DNR's Standard Survey on September 10, 2018 caught 3.58 walleye per gill net at Alton Lake. Length samples in the latest survey that recorded them ran 9–24 inches. DNR survey details →
Free interactive depth-contour map of Alton Lake, reaching a maximum surveyed depth of 70 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Minnesota DNR.
Alton Lake is a 969-acre lake in Cook County, Minnesota with a maximum depth of 72 feet. Overall water quality is declining over recent sampling years. The lake supports 7 documented fish species including northern pike, rock bass, and smallmouth bass. No public access — the lake is private or restricted.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-08-11. Methodology: how these readings are compared.
Alton Lake covers about 970 acres in Cook County. For a place on the water, look through cabin and lake-house rentals near Alton Lake on Vrbo. For a hotel or motel room, Booking.com and Expedia both search around the lake.
What Alton Lake is good for
From access and monitoring records, not editorial picks.
- Clear water13.5 ft of visibility
- Fishing7 species recorded
- Camping2 public campgrounds nearby
- Deep water72 ft surveyed max depth
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Alton Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Whether Alton 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 Alton Lake
These are the measurements Minnesota PCA publishes for Alton 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 13.5 ft. TSI 40.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 13.5ft | 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. | 40 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Alton Lake
Answers come straight from the public measurements and survey records on this page.
Minnesota DNR's Standard Survey on September 10, 2018 caught 3.58 walleye per gill net at Alton Lake. Length samples in the latest survey that recorded them ran 9–24 inches.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Alton Lake’s water-quality measurements separately, and the water-quality trend over 2 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
12 surveys on file from MN DNR Fisheries. Most recent: 2025-08-04 (Targeted Survey).
12 surveys on file · most recent 2025-08-04 (Targeted Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Tullibee (Cisco) | 18.70 | 18 in 2018-09-10 | 0.99 lb |
| White Sucker | 5.82 | 7–25 in 2018-09-10 | 2.43 lb |
| Walleye | 2.61 | 9–24 in 2018-09-10 | 2.84 lb |
| Smallmouth Bass | 2.25 | 2–18 in 2018-09-10 | 1.23 lb |
| Rock Bass | 1.80 | 4–8 in 2018-09-10 | 0.27 lb |
| Northern Pike | 0.85 | 11–23 in 2018-09-10 | 3.62 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.
Tullibee (Cisco)
White Sucker
Walleye
Smallmouth Bass
From the 2025-08-04 survey
Temperature and dissolved oxygen (DO) measurements were collected from the deepest basin in Alton Lake on August 4th, 2025, to evaluate the quantity and quality of cold, oxygenated water (i.e., oxythermal habitat) available to Cisco, also known as Tullibee, the most sensitive coldwater species present in this lake.…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Alton Lake. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — AltonFisheries Lake Survey · MN DNR LakeFinder
Lake Details
Max depth
72 ft
Surface area
969 acres
Shoreline
15.4 mi
Littoral zone
33%
Share shallower than 15 ft
Public access
No
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
11 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,798 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
Public campgrounds near Alton Lake
- Sawbill Lake Campground1.7 km
- Sawbill Lake Campground - Superior National Forest1.7 kmReserve
Nearest public campgrounds in the USGS National Map inventory, within about 3 miles. An empty list means USGS records no campground that close, which is not the same as camping being unavailable. Where the source gives an official reservation link, it is used; the cabin and hotel search does not cover campsites. More camping lakes
Stays via Stay22
Stays near Alton Lake
Compare lakeside cabins, hotels, and vacation rentals near Alton Lake in Cook 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 Alton Lake
Prices for Oct 9–11, 4 adults. Change dates on the map below.
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Fish Species
Click a species to see every lake where it is documented.
Fishing Alton Lake
Water quality readings over time
2 seasons of samples on record (2022–2024). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Worsening2 years
EPA Impairment Status
Alton 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 MN16-0622-00 · Official waterbody report
Nearby Lakes in Cook County
Frequently asked questions about Alton Lake
Where is Alton Lake?
- Alton Lake is a lake in Cook County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Alton Lake?
- Alton Lake in Cook County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 13.5 ft visibility. Maximum depth: 72 ft. Surface area: 968.63 acres.
Is Alton Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Alton Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
How deep is Alton Lake?
- Alton Lake has a maximum depth of 72 feet. The lake covers 968.63 acres.
What fish are in Alton Lake?
- Fish species found in Alton Lake include northern pike, rock bass, smallmouth bass, tullibee (cisco), walleye, white sucker, yellow perch. Alton Lake is located in Cook County, Minnesota.
What did the DNR fisheries survey find at Alton Lake?
- Minnesota DNR's Standard Survey on September 10, 2018 caught 3.58 walleye per gill net at Alton Lake. Length samples in the latest survey that recorded them ran 9–24 inches. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Alton Lake’s water-quality measurements separately, and the water-quality trend over 2 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
Can I fish at Alton Lake?
- Public access to Alton 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.
Are there campgrounds on Alton Lake?
- Alton Lake has 2 public campgrounds from USGS The National Map within 5 km, including Sawbill Lake Campground, Sawbill Lake Campground - Superior National Forest. This is a location join, not a booking. Cabins and hotels are listed separately; campsite reservations use the official link when the source provides one.
Explore Alton 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 Cook County
Species activity outlook by water temperature and season
Where to stay at Minnesota's top lakes, each with its readings
Lakes in the Lake Superior Basin (MN+WI), ranked by water quality
Minnesota's cleanest lakes, ranked on agency measurements
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Where this data comes from
2 measurements from 2 monitoring stations, 2022–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA2 samples · 2022–2024
Analytical methods
- Field measurement/observation, generic method
Monitoring station identifiers (2)
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
Public campgrounds from USGS The National Map Structures, within about 3 miles