Cook County Lake Quality

Wisconsin, 68 lakes, average grade D (Poor)

Cook County has 68 graded lakes, enough that within-county variation matters as much as the county average. Some are deep glacial basins, others are shallow agricultural-watershed waters, and the grade distribution reflects that mix. The county-wide average grade is D — water quality issues are persistent across most of the monitored basins. 26 lakes fall into the F bracket outright.

Most of the county's monitored lakes are shallow — under 50 feet — which means wind keeps the water column mixed all summer and sediment-bound phosphorus releases back into the surface layer whenever the bottom is disturbed. Diversey Harbor Lake (A) is the cleanest in the county.

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Quick Answers for Cook County

Cleanest lakes in Cook County →Cleanest lakes in Wisconsin →Safest swimming lakes in Wisconsin →

Planning a trip? Check special fishing regulations for Diversey Harbor Lake, whether the fish are safe to eat, and the best times to fish — or browse the full Wisconsin regulations index.

All Lakes in Cook County

Rank	Lake	Grade	Clarity	Max Depth	Phosphorus
1	Diversey Harbor Lake	A	25.6 ft	-	-
2	Csmi 2015 Station S Lake	A	-	-	-
3	Axehead Lake	A	11.9 ft	-	10 µg/L
4	Powderhorn Lake	A	10.1 ft	-	13 µg/L
5	Wampum Lake	B	6.9 ft	-	16 µg/L
6	Lake Calumet	B	-	-	-
7	Flatfoot Lake	B	6.3 ft	-	10.5 µg/L
8	Opeka Lake	B	3.9 ft	-	15.5 µg/L
9	Calumet Lake	B	4.3 ft	-	10.5 µg/L
10	Icebox Quarry Lake	C	9 ft	-	-
11	Forge Quarry Lake	C	8.5 ft	-	-
12	Sag Quarry East Lake	C	5.4 ft	-	30.5 µg/L
13	Turtlehead Lake	C	2.8 ft	-	20.5 µg/L
14	Sag Quarry West Lake	C	4.2 ft	-	52.5 µg/L
15	Lake Opeka	D	4 ft	-	-
16	Consumers Quarry Lake	D	6.5 ft	-	-
17	Lake Arlington	D	4.5 ft	-	-
18	Great Lakes Quarries East	D	4.5 ft	-	-
19	Flatfoot Lake	D	6 ft	-	-
20	Papoose Lake	D	5 ft	-	-
21	Maple Lake	D	5 ft	-	-
22	Horsetail Lake	D	5 ft	-	-
23	Sag Quarry-West Lake	D	5.5 ft	-	-
24	Doughnut Lake	D	5 ft	-	-
25	Busse Lake Main Pool	D	3.5 ft	-	-
26	Lake Glenview	D	3.3 ft	-	-
27	Pogie Lake	D	3.5 ft	-	-
28	Columbia Basin Lake	D	6 ft	-	-
29	Jackson Park Inner Harbor Lake	D	5 ft	-	-
30	Turtlehead Lake	D	6 ft	-	-
31	Jackson Park West Lagoon Lake	D	5 ft	-	-
32	Jackson Park Outer Harbor Lake	D	6 ft	-	-
33	59th Street Harbor Lake	D	6 ft	-	-
34	South Pond	D	5.3 ft	-	-
35	Jackson Park East Lagoon Lake	D	5 ft	-	-
36	Skokie Lagoon 5 Lake	D	3.5 ft	-	-
37	Skokie Lagoon 6 Lake	D	4 ft	-	-
38	Arrowhead Lake	D	2.1 ft	-	31.5 µg/L
39	Bullfrog Lake	D	1.4 ft	-	40.5 µg/L
40	Horsetail Lake	D	2.2 ft	-	39 µg/L
41	Tampier Lake	D	1.7 ft	-	38.5 µg/L
42	Midlothian Lake	D	1.2 ft	-	44.5 µg/L
43	Lake Charlemagne	F	2 ft	-	-
44	Bode Lake North	F	1.5 ft	-	-
45	Great Lakes Quarries West	F	2.5 ft	-	-
46	Bull Frog Lake	F	3 ft	-	-
47	Belly Deep Slough Lake	F	0.7 ft	-	-
48	Sauk Lake	F	1 ft	-	-
49	Crabtree Lake	F	2 ft	-	-
50	North Pond	F	2.5 ft	-	-
51	Washington Park Lagoon Lake	F	1.4 ft	-	-
52	Skokie Lagoon 7 Lake	F	1.5 ft	-	-
53	Sherman Park Lagoon Lake	F	1.3 ft	-	-
54	Tampier Lake	F	2 ft	-	-
55	Humboldt Park Lagoon Lake	F	1.5 ft	-	-
56	Skokie Lagoon 2 Lake	F	1 ft	-	-
57	Skokie Lagoon 1 Lake	F	1 ft	-	-
58	Big Marsh Park Ne Lake	F	2.3 ft	-	-
59	Garfield Park Lagoon Lake	F	1.5 ft	-	-
60	Douglass Park Lagoon Lake	F	1.5 ft	-	-
61	Mckinley Park Lagoon Lake	F	1.5 ft	-	-
62	Columbus Park Lagoon Lake	F	2.5 ft	-	-
63	Marquette Park Lagoon Lake	F	3 ft	-	-
64	Burnham Prairie Marsh West Lake	F	3.1 ft	-	-
65	Big Marsh Lake	F	1 ft	-	-
66	Lake Calumet	F	3 ft	-	-
67	Saganashkee Slough Lake	F	0.8 ft	-	93.5 µg/L
68	Skokie Lagoons Lake	F	1.6 ft	-	155 µg/L

Source: EPA National Aquatic Resource Surveys, 2026.