Mill Lake
Mill Lake in Walworth County, Wisconsin has a water quality grade of B (Good). Water clarity: 7.5 ft visibility. Phosphorus: 15.3 µg/L. Maximum depth: 40 ft. Surface area: 271 acres.
Wisconsin DNR lists Panfish as common on Mill Lake. DNR survey details →
- Clarity
- 7.5 ft
- Max depth
- 40 ft
- Area
- 271 acres
- Type
- Mesotrophic
- Trend
- ↑ Improving
- Public access
- Yes
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Mill Lake is a 271-acre mesotrophic lake in Walworth County, Wisconsin with a maximum depth of 40 feet. Water quality is graded B based on 1 sampling years through 2026. Overall water quality is improving over recent sampling years. The lake supports 4 documented fish species including Panfish, Largemouth Bass, and Northern Pike. Public access is available with 2 public boat landings. Compared to the 18 other monitored lakes in Walworth County, Mill Lake ranks #11 for water quality.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-06-12. Grade methodology: LakeQuality methodology.
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Swimming Safety
Grade onlyLow algae
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Good for swimming, clear water with low algae levels
Water Quality Grade: B (Good)
Moderate clarity, visible to about 7.5 ft. Phosphorus level: 15.3 µg/L. Trophic State Index: 46.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 7.5 ft | Not graded |
| Phosphorus | 15.3 µg/L | Good |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 46 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Mill Lake
Compare lakeside cabins, hotels, and vacation rentals near Mill Lake in Walworth County, Wisconsin — 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 Mill Lake
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Planning a whole trip? See where to stay at Wisconsin’s top lakes →
Wisconsin DNR lists Panfish as common on Mill Lake.
A DNR fisheries survey reports fish abundance and catch rates, not a water-quality grade. LakeQuality grades Mill Lake B from EPA Water Quality Portal chemistry, and the water-quality trend over 7 years of monitoring is improving. Catch rate is not a swim clearance and is not a weekly bite report.
WI DNR Lake Profile
Authoritative data from the Wisconsin DNR LakePages. Monitored by volunteers since 2006. 1 station on file (most recent sample 2025).
Fish Species (DNR-rated)
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 40 ft |
| Surface Area | 271 acres |
| Public Access | Yes |
Recreation & Access
- Ridge RoadPublic
- SterlingworthPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Mill Lake
Invasive & Introduced Species
Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.
Water Quality Trend: ↑ Improving
Based on 7 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.307 m/yr | 7 |
| Phosphorus | → Stable | +0.07 µg/L/yr | 7 |
Reservoir Info (USACE NID)
Mill Lake is a man-made reservoir impounded by the Lauderdale Lakes (completed 1840), built primarily for recreation on the Honey Creek; gravity-type dam, 14 ft tall and 425 ft long.
- Surface area
- 834 ac
- Normal storage
- 5,500 ac-ft
- Max storage
- 7,200 ac-ft
- Drainage area
- 12 sq mi
- Hazard class
- High
- Owner
- Lauderdale Lakes Lake Management District
Source: USACE National Inventory of Dams, NID ID WI00212 · Operator website · Matched by proximity (0.78 km)
County Ranking
Ranked #11 of 19 lakes in Walworth County
Nearby Lakes in Walworth County
Frequently asked questions about Mill Lake
Where is Mill Lake?
- Mill Lake is a lake in Walworth County, Wisconsin. LakeQuality grades it B for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Mill Lake?
- Mill Lake in Walworth County, Wisconsin has a water quality grade of B (Good). Water clarity: 7.5 ft visibility. Phosphorus: 15.3 µg/L. Maximum depth: 40 ft. Surface area: 271 acres.
Is Mill Lake safe to swim in?
- Good for swimming, clear water with low algae levels. Mill Lake has a water quality grade of B (Good). Always check local health department advisories before swimming.
How deep is Mill Lake?
- Mill Lake has a maximum depth of 40 feet. The lake covers 271 acres.
What fish are in Mill Lake?
- Fish species found in Mill Lake include Panfish, Largemouth Bass, Northern Pike, Walleye. Mill Lake is located in Walworth County, Wisconsin.
What did the DNR fisheries survey find at Mill Lake?
- Wisconsin DNR lists Panfish as common on Mill Lake. A DNR fisheries survey reports fish abundance and catch rates, not a water-quality grade. LakeQuality grades Mill Lake B from EPA Water Quality Portal chemistry, and the water-quality trend over 7 years of monitoring is improving. Catch rate is not a swim clearance and is not a weekly bite report.
Are there boat ramps on Mill Lake?
- Mill Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Ridge Road, Sterlingworth. Public access is listed as yes.
Explore Mill Lake across LakeQuality
Depth, room, public access, and the state wake-sport rules
Fish species and top-graded lakes across Wisconsin
Fish species and best lakes in Walworth County
Species activity outlook by water temperature and season
Where to stay at Wisconsin's top lakes, each with its grade
Moderate nutrients, good water quality
Wisconsin's cleanest and most-polluted lakes, ranked
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State Parks Near Mill Lake
Other Grade B Lakes in Wisconsin
Mesotrophic Lakes in Wisconsin
Where this data comes from
64 measurements from 1 monitoring station, 2020–2026. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Wisconsin Department of Natural Resources
WIDNR_WQX64 samples · 2020–2026
Analytical methods
- Phosphorus by Colorimetry
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Fish and recreation data from Wisconsin DNR Lakes
Named boat-access points from the USGS National Boat Ramps inventory