Deep Lakes in Minnesota & Wisconsin

Q: Why are deep lakes important for water quality?

Deep lakes maintain a thermocline (temperature barrier) that keeps bottom water cold and oxygen-rich throughout summer. This supports coldwater fish species like lake trout and cisco that cannot survive in shallower, warmer lakes. Deep lakes also resist algae blooms better because their large volume dilutes nutrients.

Q: What is the deepest lake in Minnesota and Wisconsin?

The deepest lakes in both states exceed 200 feet. These deep lakes are typically located in geologically carved basins from glacial activity and offer some of the best water quality and coldwater fishing in the region.

Lakes over 50 feet deep in Minnesota and Wisconsin. Deep lakes maintain cold, oxygenated water below the thermocline year-round, supporting coldwater species like lake trout, cisco, and whitefish.

Maximum-depth data currently comes from the Minnesota and Wisconsin DNR lake surveys, so these rankings cover MN and WI lakes only. Grades for the other 10 covered states are based on clarity and nutrient measurements.

Deep (50+ ft)Medium (20-50 ft)Shallow (<20 ft)

100

Total Lakes

Minnesota

Wisconsin

Rank	Lake	County	State	Grade	Depth	Area	Fish
1	Gilbert Pit Lake	St. Louis	MN	B	443 ft	243 acres	10
2	St James Pit Lake	St. Louis	MN	A	381 ft	124 acres	5
3	Wazee Lake	Jackson	WI	A	350 ft	146 acres	0
4	Iron Chief Complex Lake	St. Louis	MN	A	262.1 ft	207 acres	3
5	Green Lake	Green Lake	WI	B	236 ft	7,920 acres	7
6	Green Lake	Green Lake	WI	B	236 ft	7,920 acres	7
7	Green Lake	Green Lake	WI	C	236 ft	7,920 acres	7
8	Green Lake	Green Lake	WI	B	236 ft	7,920 acres	7
9	Green Lake East Basin	Green Lake	WI	B	236 ft	7,920 acres	7
10	Silver Creek Estuary Lake	Green Lake	WI	F	236 ft	7,920 acres	7
11	City Millpond	Green Lake	WI	C	236 ft	7,920 acres	7
12	Lasalle Lake	Hubbard	MN	B	213 ft	238 acres	15
13	Watap Lake	Cook	MN	C	210 ft	1,993 acres	1
14	Sagamore Mine Lake	Crow Wing	MN	A	210 ft	119 acres	11
15	Gabimichigami Lake	Cook	MN	B	209 ft	1,186 acres	0
16	Ten Mile Lake	Cass	MN	A	208 ft	5,080 acres	17
17	Loon Lake	Cook	MN	A	202 ft	1,095 acres	10
18	Gunflint Lake	Cook	MN	A	200 ft	4,009 acres	12
19	Little Gunflint Lake	Cook	MN	A	200 ft	4,009 acres	12
20	Strup Lake	Lake	MN	B	195 ft	1,689 acres	5
21	Sand Point Lake	St. Louis	MN	C	184 ft	8,527 acres	21
22	Sand Point Lake	St. Louis	MN	D	184 ft	8,527 acres	21
23	Sand Point Lake	St. Louis	MN	D	184 ft	8,527 acres	21
24	Larson Lake	Itasca	MN	A	177 ft	208 acres	6
25	Lac la Croix Lake	St. Louis	MN	C	168 ft	29,597 acres	12
26	Crooked Lake	Lake	MN	C	165 ft	10,360 acres	0
27	Carlos Lake	Douglas	MN	A	163 ft	2,605 acres	21
28	Alvin Lake	Douglas	MN	B	163 ft	2,605 acres	21
29	Rainy Lake	Koochiching	MN	D	161 ft	210,200 acres	17
30	Rainy Lake	St. Louis	MN	D	161 ft	210,200 acres	17
31	Rainy Lake	St. Louis	MN	C	161 ft	210,200 acres	17
32	Rainy Lake	St. Louis	MN	C	161 ft	210,200 acres	17
33	Rainy Lake	Koochiching	MN	D	161 ft	210,200 acres	17
34	Rainy Lake	Koochiching	MN	D	161 ft	210,200 acres	17
35	Rainy Lake	Koochiching	MN	D	161 ft	210,200 acres	17
36	Rainy Lake	Koochiching	MN	D	161 ft	210,200 acres	17
37	Rainy Lake	Koochiching	MN	C	161 ft	210,200 acres	17
38	Trout Lake	Itasca	MN	A	157 ft	1,743 acres	9
39	Caribou Lake	Itasca	MN	A	152 ft	247 acres	7
40	Namakan Lake	St. Louis	MN	C	150 ft	24,066 acres	18
41	Namakan Lake	St. Louis	MN	C	150 ft	24,066 acres	18
42	Namakan Lake	St. Louis	MN	D	150 ft	24,066 acres	18
43	Little Saganaga Lake	Cook	MN	C	150 ft	1,627 acres	5
44	Namakan Lake	St. Louis	MN	B	150 ft	24,066 acres	18
45	Snowbank Lake	Lake	MN	A	150 ft	4,655 acres	11
46	Steamboat Bay Lake	Cass	MN	B	150 ft	103,444 acres	18
47	Kabekona Bay Lake	Cass	MN	A	150 ft	103,444 acres	18
48	Six Lake	Otter Tail	MN	A	140 ft	197 acres	11
49	Elmo Lake	Washington	MN	A	140 ft	257 acres	13
50	South Lake	Cook	MN	A	140 ft	1,145 acres	6
51	Miner'S Pit West Lake	St. Louis	MN	A	140 ft	141 acres	9
52	Whitefish Lake	Crow Wing	MN	A	138 ft	7,714 acres	23
53	Rose Lake	Otter Tail	MN	A	137 ft	1,200 acres	17
54	Long Lake	Hubbard	MN	A	135 ft	1,926 acres	14
55	Trout Lake	Itasca	MN	A	135 ft	1,862 acres	15
56	Big Sand Lake	Hubbard	MN	A	135 ft	1,639 acres	16
57	Geneva Lake	Walworth	WI	A	135 ft	5,401 acres	6
58	Geneva Lake	Walworth	WI	A	135 ft	5,401 acres	6
59	Geneva Lake Site B	Walworth	WI	A	135 ft	5,401 acres	6
60	Outlet To Lake Geneva	Walworth	WI	F	135 ft	5,401 acres	6
61	Kabekona Lake	Hubbard	MN	A	133 ft	2,433 acres	20
62	Koronis Lake	Stearns	MN	C	132 ft	2,968 acres	22
63	Rose Lake	Cook	MN	B	130 ft	477 acres	5
64	Duncan Lake	Cook	MN	A	130 ft	477 acres	5
65	Kekekabic Lake	Lake	MN	A	130 ft	55 acres	0
66	Kek Lake	Lake	MN	A	130 ft	55 acres	0
67	Oyster Lake	St. Louis	MN	D	130 ft	763 acres	0
68	Mountain Lake	Unknown	MN	A	130 ft	1,344 acres	7
69	Rove Lake	Cook	MN	C	130 ft	1,344 acres	7
70	Roosevelt Lake	Cass	MN	A	129 ft	1,511 acres	18
71	Long Lake	Otter Tail	MN	B	128 ft	1,289 acres	16
72	Big Trout Lake	Crow Wing	MN	A	128 ft	1,366 acres	20
73	Burntside Lake	St. Louis	MN	A	126 ft	7,314 acres	15
74	Round Lake	Aitkin	MN	A	125 ft	737 acres	18
75	Jasper Lake	Cook	MN	B	125 ft	246 acres	0
76	Mina Lake	Douglas	MN	A	123 ft	411 acres	18
77	Big Watab Lake	Stearns	MN	A	123 ft	246 acres	15
78	Deer Lake	Itasca	MN	A	121 ft	4,093 acres	17
79	Bluewater Lake	Itasca	MN	A	120 ft	364 acres	15
80	Otter Tail Lake	Otter Tail	MN	A	120 ft	14,079 acres	17
81	White Earth Lake	Becker	MN	A	120 ft	1,989 acres	17
82	Becker Lake	Becker	MN	D	120 ft	1,989 acres	17
83	Peter Lake	Cook	MN	A	120 ft	282 acres	4
84	Drewery Lake	Beltrami	MN	B	120 ft	15,958 acres	21
85	West Pike Lake	Cook	MN	A	120 ft	788 acres	5
86	Cass Lake Allens Bay	Beltrami	MN	A	120 ft	15,958 acres	21
87	Cass Lake	Beltrami	MN	A	120 ft	15,958 acres	21
88	Elkhart Lake	Sheboygan	WI	A	119 ft	292 acres	7
89	Long Lake	Aitkin	MN	B	116 ft	435 acres	16
90	Ima Lake	Lake	MN	B	116 ft	742 acres	0
91	Long Lake	Cass	MN	A	115 ft	1,007 acres	14
92	Wabana Lake	Itasca	MN	A	115 ft	2,221 acres	14
93	Long Lake	Cass	MN	A	115 ft	1,007 acres	14
94	Minnetonka Lake	Hennepin	MN	B	113 ft	14,206 acres	18
95	Pine Lake	Cook	MN	A	113 ft	2,122 acres	10
96	Pokegama Lake	Itasca	MN	A	112 ft	6,721 acres	19
97	Pokegama Lake	Itasca	MN	A	112 ft	6,721 acres	19
98	Greenwood Lake	Cook	MN	A	112 ft	2,043 acres	10
99	Rabideau Lake	Beltrami	MN	C	112 ft	680 acres	14
100	Washburn Lake	Cass	MN	A	111 ft	1,590 acres	21

Frequently Asked Questions

Why are deep lakes important for water quality?

Deep lakes maintain a thermocline (temperature barrier) that keeps bottom water cold and oxygen-rich throughout summer. This supports coldwater fish species like lake trout and cisco that cannot survive in shallower, warmer lakes. Deep lakes also resist algae blooms better because their large volume dilutes nutrients.

What is the deepest lake in Minnesota and Wisconsin?

The deepest lakes in both states exceed 200 feet. These deep lakes are typically located in geologically carved basins from glacial activity and offer some of the best water quality and coldwater fishing in the region.

Notable Deep Lakes

Gilbert Pit Lake

St. Louis County, MN · Grade B · 443 ft

St James Pit Lake

St. Louis County, MN · Grade A · 381 ft

Wazee Lake

Jackson County, WI · Grade A · 350 ft

Iron Chief Complex Lake

St. Louis County, MN · Grade A · 262.1 ft

Green Lake

Green Lake County, WI · Grade B · 236 ft

Green Lake

Green Lake County, WI · Grade B · 236 ft

Source: EPA National Aquatic Resource Surveys, 2026.