Cook County Lake Quality

Minnesota, 128 lakes, average grade C (Fair)

Cook County has 128 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. Cook County averages to a C. The distribution behind that average matters more than the letter: a few stressed lakes versus many decent ones can produce the same average as the inverse.

Many of the county's lakes are deep glacial basins — over 50 feet at their deepest point — which gives them thermal stratification and a buffer against summer warming. Clearwater Lake (grade A) is the cleanest in the county.

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Quick Answers for Cook County

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

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

DNR Reports (160)

Minnesota DNR LakeFinder resources for lakes in Cook County. Showing 12 most recent — browse all reports →

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Fisheries Lake Survey — West Twin
Fisheries Lake Survey · MN DNR LakeFinder
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Fisheries Lake Survey — West Pike
Fisheries Lake Survey · MN DNR LakeFinder
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Fisheries Lake Survey — Mountain
Fisheries Lake Survey · MN DNR LakeFinder
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Fisheries Lake Survey — Ward
Fisheries Lake Survey · MN DNR LakeFinder
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Fisheries Lake Survey — Two Island
Fisheries Lake Survey · MN DNR LakeFinder
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Fisheries Lake Survey — Trout
Fisheries Lake Survey · MN DNR LakeFinder
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Fisheries Lake Survey — Tom
Fisheries Lake Survey · MN DNR LakeFinder
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Fisheries Lake Survey — Crooked
Fisheries Lake Survey · MN DNR LakeFinder
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Fisheries Lake Survey — Tait
Fisheries Lake Survey · MN DNR LakeFinder
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Fisheries Lake Survey — Star
Fisheries Lake Survey · MN DNR LakeFinder
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Fisheries Lake Survey — South
Fisheries Lake Survey · MN DNR LakeFinder
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Fisheries Lake Survey — Gull
Fisheries Lake Survey · MN DNR LakeFinder

All Lakes in Cook County

Rank	Lake	Grade	Clarity	Max Depth	Phosphorus
1	Clearwater Lake	A	30 ft	65 ft	4 µg/L
2	Birch Lake	A	18 ft	69 ft	8 µg/L
3	Round Lake	A	16.5 ft	45 ft	8.5 µg/L
4	Pike Lake	A	17.8 ft	45 ft	6 µg/L
5	Trout Lake	A	19 ft	77 ft	9 µg/L
6	Gull Lake	A	16.4 ft	-	9 µg/L
7	Hungry Jack Lake	A	18 ft	71 ft	7 µg/L
8	Pine Lake	A	18 ft	113 ft	-
9	Leo Lake	A	15 ft	28 ft	-
10	Duncan Lake	A	22 ft	130 ft	-
11	Lone Lake	A	21 ft	-	-
12	Mayhew Lake	A	20.6 ft	84 ft	5 µg/L
13	Loon Lake	A	18 ft	202 ft	5 µg/L
14	Gunflint Lake	A	20 ft	200 ft	-
15	Kemo Lake	A	17 ft	65 ft	-
16	Flour Lake	A	18.5 ft	75 ft	7 µg/L
17	Bearskin Lake	A	21.3 ft	78 ft	6 µg/L
18	Peter Lake	A	22.5 ft	120 ft	-
19	Canoe Lake	A	20.5 ft	40 ft	-
20	Su18 Lake	A	38.7 ft	-	-
21	Mcfarland Lake	A	17 ft	-	9 µg/L
22	Chester Lake	A	39 ft	-	-
23	Su19 Lake	A	37.7 ft	-	-
24	16-0023-00 Lake	A	17 ft	35 ft	-
25	Little Gunflint Lake	A	16.2 ft	200 ft	7 µg/L
26	Rog Lake	A	26.2 ft	40 ft	-
27	16-0524-00 Lake	A	15 ft	142 ft	-
28	Superior Lake	A	15.1 ft	-	4 µg/L
29	West Pike Lake	A	19 ft	120 ft	-
30	Taylor Lake Deep	A	10.6 ft	-	13 µg/L
31	Trout Lake Deep	A	10.7 ft	-	9.7 µg/L
32	Poplar Lake	A	10.2 ft	30 ft	10 µg/L
33	Sea Gull Lake	A	14.5 ft	40 ft	7 µg/L
34	Two Island Lake	A	10.5 ft	27 ft	14 µg/L
35	Saganaga Lake	A	12 ft	-	7 µg/L
36	Greenwood Lake	A	14.8 ft	112 ft	8 µg/L
37	Gogebic Lake	A	13.8 ft	61 ft	5 µg/L
38	Alder Lake	A	13.8 ft	72 ft	8 µg/L
39	West Twin Lake	B	9.8 ft	37 ft	9 µg/L
40	Portage Lake	B	8.5 ft	55 ft	9.5 µg/L
41	Caribou Lake	B	7 ft	-	15 µg/L
42	Devil Track Lake	B	7 ft	50 ft	12.5 µg/L
43	Esther Lake	B	10 ft	35 ft	-
44	Red Rock Lake	B	12.7 ft	64 ft	-
45	Deer Yard Lake	B	7.5 ft	20 ft	15 µg/L
46	East Bearskin Lake	B	14 ft	66 ft	-
47	Owl Lake	B	13 ft	70 ft	-
48	Rose Lake	B	14.5 ft	130 ft	-
49	Tom Lake	B	9 ft	35 ft	8 µg/L
50	Tait Lake	B	7.1 ft	15 ft	12.5 µg/L
51	Brule Lake	B	10 ft	78 ft	-
52	Jasper Lake	B	12 ft	125 ft	-
53	Ball Club Lake	B	9.5 ft	25 ft	16.5 µg/L
54	Alpine Lake	B	12 ft	65 ft	-
55	Clara Lake	B	7.6 ft	15 ft	15 µg/L
56	Mesaba Lake	B	10 ft	65 ft	-
57	Alton Lake	B	13.5 ft	72 ft	-
58	Beth Lake	B	11.1 ft	22 ft	-
59	Taylor Lake Inlet_1	B	11.3 ft	-	-
60	Dick Lake	B	7.7 ft	12 ft	10 µg/L
61	Tarry Lake	B	13 ft	66 ft	-
62	Gabimichigami Lake	B	14 ft	209 ft	-
63	East Pike Lake	B	12.2 ft	40 ft	-
64	Chevans Lake Deep	B	1.9 ft	-	17.5 µg/L
65	Little Lake Deep	B	-324.8 ft	-	14 µg/L
66	North Lake Deep	B	-324.8 ft	-	7.7 µg/L
67	Rice Lake	B	5.7 ft	10 ft	17 µg/L
68	East Twin Lake	B	6.2 ft	19 ft	17 µg/L
69	Elbow Lake	B	3.7 ft	9 ft	19 µg/L
70	Ward Lake	B	5.6 ft	13 ft	16.5 µg/L
71	Ella Lake	B	6 ft	-	4 µg/L
72	Missouri Lake	B	4.1 ft	-	11 µg/L
73	Turtle Lake Deep	C	-324.8 ft	-	22 µg/L
74	Teal Lake Deep	C	3.3 ft	-	15.5 µg/L
75	Horseshoe Lake	C	7 ft	26 ft	-
76	Caribou Lake	C	8 ft	26 ft	-
77	Lizz Lake	C	9 ft	30 ft	-
78	Copper Lake	C	7 ft	52 ft	-
79	Little Saganaga Lake	C	9.3 ft	150 ft	-
80	Gust Lake	C	7 ft	-	-
81	Mora Lake	C	8.5 ft	40 ft	-
82	Davis Lake	C	8.9 ft	64 ft	-
83	Phoebe Lake	C	7.5 ft	25 ft	-
84	Loon Lake Deep	C	-324.8 ft	-	23 µg/L
85	Karl Lake	C	8 ft	70 ft	-
86	16-0569-00 Lake	C	9.5 ft	95 ft	-
87	South Lake	C	8 ft	140 ft	-
88	Dyers Lake	C	4.9 ft	23 ft	21.5 µg/L
89	Cross Bay Lake	C	7 ft	-	-
90	Sawbill Lake	C	6.8 ft	45 ft	-
91	Swamp Lake Deep	C	1.7 ft	-	27 µg/L
92	Rove Lake	C	9 ft	130 ft	-
93	Watap Lake	C	9 ft	210 ft	-
94	Long Island Lake	C	8 ft	85 ft	-
95	Mt Maud Lake	C	3.4 ft	-	34 µg/L
96	Helmer_nelson Pond Deep	C	2.5 ft	-	60 µg/L
97	Cuffs Lake Deep	C	-324.8 ft	-	31 µg/L
98	Dutchman Lake Deep	D	2.3 ft	-	31 µg/L
99	Ada Lake	D	5.5 ft	13 ft	-
100	Star Lake	D	4.9 ft	13 ft	-
101	Homer Lake	D	6 ft	22 ft	-
102	Onagon Lake	D	6 ft	15 ft	-
103	Holly Lake	D	4.9 ft	6 ft	-
104	Hub Lake	D	4.5 ft	-	-
105	Mt Maud Lake Inlet	D	3.4 ft	-	-
106	Cuffs Lake Landing	D	4.9 ft	-	-
107	Lower George Lake	D	3.5 ft	-	-
108	Center Lakedeep	D	1.4 ft	-	53 µg/L
109	Chevans Lake Beaver 2	F	1.9 ft	-	-
110	Chevans Lake Y	F	1.9 ft	-	-
111	Mt Maud Lake Mid Basin	F	2.5 ft	-	-
112	Swede Lake Deep	F	-324.8 ft	-	-
113	Chevans Lake Inlet 1	F	1.9 ft	-	-
114	Mt Maud Lake Beaver Dam	F	2.9 ft	-	-
115	Dutchman Lake Inlet 2	F	2 ft	-	-
116	Center Lakelanding	F	-161.7 ft	-	-
117	Helmer_nelson Pond Middle	F	2.5 ft	-	-
118	Dutchman Lakelanding	F	2.3 ft	-	-
119	Chaser Lake	F	1 ft	65 ft	-
120	Helmer_nelson Pond Inlet	F	2.3 ft	-	-
121	Mt Maud Lake W_edge_basin	F	2.5 ft	-	-
122	Helmer_nelson Pond East End Beaver House	F	2.5 ft	-	-
123	Turtle Lake Inlet	F	-324.8 ft	-	-
124	Swede Lake Outlet	F	-324.8 ft	-	-
125	Swede Lake Inlet	F	-324.8 ft	-	-
126	Turtle Lake East End	F	-324.8 ft	-	-
127	Little Lake Inlet	F	-324.8 ft	-	-
128	Little Lake Landing	F	-324.8 ft	-	-

Source: EPA National Aquatic Resource Surveys, 2026.