Little Boy Lake
Cass County, Minnesota1,452 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Little Boy Lake. Here is what has been measured.
- Mesotrophic
- Impaired · Mercury
- 74 ft max depth
- Public access
Little Boy Lake in Cass County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 11 ft visibility. Phosphorus: 14 µg/L. Chlorophyll-a (algae): 5.1 µg/L. Maximum depth: 74 ft. Surface area: 1451.67 acres.
Minnesota DNR's Standard Survey on June 24, 2024 caught 9.83 walleye per gill net at Little Boy Lake. Length samples in the latest survey that recorded them ran 5–25 inches. DNR survey details →
Free interactive depth-contour map of Little Boy Lake, reaching a maximum surveyed depth of 70 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Minnesota DNR.
Little Boy Lake is a 1,452-acre mesotrophic lake in Cass County, Minnesota with a maximum depth of 74 feet. Phosphorus level is declining over recent sampling years. The lake supports 18 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 2 public boat landings. Compared to the 103 other monitored lakes in Cass County, Little Boy Lake ranks #36 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-29. Methodology: how these readings are compared.
Little Boy Lake covers about 1,500 acres in Cass County. It has 2 public boat landings, so a lakefront rental is not the only way to get a boat on the water. The median ice-out date is April 23, which is when the open-water season begins. For a place on the water, look through cabin and lake-house rentals near Little Boy Lake on Vrbo. For a hotel or motel room, Booking.com and Expedia both search around the lake.
What Little Boy Lake is good for
From access and monitoring records, not editorial picks.
- Clear water11 ft of visibility
- Boat launch2 documented ramps
- Fishing18 species recorded
- Ice seasonIce-out around Apr 23
- Deep water74 ft surveyed max depth
- Big water1,452 acres
Swimming conditions
Readings onlyLow algae
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Little Boy Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Whether Little Boy 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 Little Boy Lake
These are the measurements Minnesota PCA publishes for Little Boy 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 11 ft. Phosphorus 14 µg/L. Chlorophyll-a 5.1 µg/L. TSI 44.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 11ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 14µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 5.1µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 44 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Little Boy Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Little Boy Lake typically sits around 67°F at the surface in September. Summer average is about 66°F. Usually warmest in Jul (about 71°F) and coldest in May (about 57°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (57°F) to its warmest (71°F).
Typical surface water temperature by month, from 170 field readings (2016–2025) via the EPA Water Quality Portal. See the full Little Boy Lake water temperature breakdown →
Minnesota DNR's Standard Survey on June 24, 2024 caught 9.83 walleye per gill net at Little Boy Lake. Length samples in the latest survey that recorded them ran 5–25 inches.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Little Boy Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is stable. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
19 surveys on file from MN DNR Fisheries. Most recent: 2024-07-29 (Targeted Survey).
19 surveys on file · most recent 2024-07-29 (Targeted Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Yellow Perch | 18.68 | 4–10 in 2024-06-24 | 0.14 lb |
| Walleye | 12.60 | 5–25 in 2024-06-24 | 1.79 lb |
| Bluegill | 8.06 | 1–8 in 2024-06-24 | 0.18 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.
Yellow Perch
Walleye
Bluegill
From the 2024-07-29 survey
Temperature and dissolved oxygen profiles were collected in the deepest basins in Little Boy Lake on July 30, 2024 , 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. Cisco…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Little Boy Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — Little BoyFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Little Boy (1529)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — Little BoyFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — Little BoyPublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
74 ft
Surface area
1,452 acres
Shoreline
10 mi
Littoral zone
32%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
29 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,302 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Little Boy LakePublic
- Little Boy Resort & CampgroundSemi-private
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Little Boy Lake
Compare lakeside cabins, hotels, and vacation rentals near Little Boy Lake in Cass 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 Little Boy 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 Little Boy Lake’s readings
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Fish Species
Click a species to see every lake where it is documented.
Fishing Little Boy Lake
Water Quality Trend: Stable
Based on 6 years of monitoring (2020–2025).
Water clarity
Stable6 years
Phosphorus
Worsening+0.63 µg/L/yr6 years
Chlorophyll-a
Improving-0.25 µg/L/yr6 years
Ice season
Typical ice-out
Apr 23
Earliest Mar 27, 2012 · Latest May 13, 2013
Typical ice-in
Dec 1
Earliest Nov 20, 2018 · Latest Dec 28, 2015
Most recent ice-out
May 3
2023
42 observations · Minnesota PCA ice records
EPA Impairment Status
Little Boy 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 MN11-0167-00 · Official waterbody report
Nearby Lakes in Cass County
Frequently asked questions about Little Boy Lake
Where is Little Boy Lake?
- Little Boy Lake is a lake in Cass County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Little Boy Lake?
- Little Boy Lake in Cass County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 11 ft visibility. Phosphorus: 14 µg/L. Chlorophyll-a (algae): 5.1 µg/L. Maximum depth: 74 ft. Surface area: 1451.67 acres.
Is Little Boy Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Little Boy 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 Little Boy Lake?
- Little Boy Lake typically sits around 67°F at the surface in September, from 170 EPA Water Quality Portal field readings (2016–2025). That is a typical value for the month, not a live reading.
How deep is Little Boy Lake?
- Little Boy Lake has a maximum depth of 74 feet. The lake covers 1451.67 acres.
What fish are in Little Boy Lake?
- Fish species found in Little Boy Lake include black bullhead, black crappie, bluegill, bowfin (dogfish), brown bullhead, cisco species, hybrid sunfish, largemouth bass, muskellunge, northern pike, pumpkinseed, rock bass, smallmouth bass, tullibee (cisco), walleye, white sucker, yellow bullhead, yellow perch. Little Boy Lake is located in Cass County, Minnesota.
What did the DNR fisheries survey find at Little Boy Lake?
- Minnesota DNR's Standard Survey on June 24, 2024 caught 9.83 walleye per gill net at Little Boy Lake. Length samples in the latest survey that recorded them ran 5–25 inches. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Little Boy Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is stable. Catch rate is not a swim clearance and is not a weekly bite report.
When does Little Boy Lake thaw?
- Little Boy Lake typically has ice-out around Apr 23. Ice typically forms around Dec 1. The open water season is approximately 222 days.
Are there boat ramps on Little Boy Lake?
- Little Boy Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Little Boy Lake, Little Boy Resort & Campground. Public access is listed as yes.
Can I fish at Little Boy Lake?
- Little Boy Lake has 2 documented boat landings 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 Little Boy Lake across LakeQuality
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Where this data comes from
188 measurements from 1 monitoring station, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA188 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
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
Named boat-access points from the USGS National Boat Ramps inventory
Ice data from Minnesota DNR Climate