Updated August 2026

Deepest Lakes by Maximum Depth

The 50 deepest lakes ranked by maximum depth in feet, from DNR bathymetric surveys. Deeper lakes tend to hold better water quality — thermal stratification keeps bottom nutrients from mixing up to the sunlit surface where they would feed algae. Depth data currently covers Minnesota and Wisconsin; water-quality grades and clarity for all 38 states are on each state page.

The deepest lake on the index is Gilbert Pit Lake in St. Louis County, MN, at 443 ft. The deepest waters in the region are split between natural Boundary Waters and Northwoods lakes and a handful of flooded iron-ore mine pits, which plunge to extreme depths in a small footprint.

The deepest lake in Minnesota is Gilbert Pit Lake in St. Louis County, at 443 ft (water-quality grade ). The deepest lake in Wisconsin is Wazee Lake in Jackson County, at 350 ft (grade ).

Depth figures come from state DNR lake-survey morphology; water-quality grades and Secchi clarity come from EPA National Aquatic Resource Surveys and state monitoring programs.

Top 3 Deepest Lakes

#1NR

Gilbert Pit Lake

St. Louis County, MN

Max depth 443 ft, Grade . Clarity 11.5 ft.

#2NR

St James Pit Lake

St. Louis County, MN

Max depth 381 ft, Grade . Clarity 47.6 ft.

#3NR

Wazee Lake

Jackson County, WI

Max depth 350 ft, Grade . Clarity 30 ft.

Rank	Lake	County	State	Max Depth	Area	Grade	Clarity
1	Gilbert Pit Lake	St. Louis	MN	443 ft	243 acres	NR	11.5 ft
2	St James Pit Lake	St. Louis	MN	381 ft	124 acres	NR	47.6 ft
3	Wazee Lake	Jackson	WI	350 ft	146 acres	NR	30 ft
4	Iron Chief Complex Lake	St. Louis	MN	262.1 ft	207 acres	NR	24.5 ft
5	Green Lake	Green Lake	WI	236 ft	7,920 acres	A	13.5 ft
6	Lasalle Lake	Hubbard	MN	213 ft	238 acres	A	6.9 ft
7	Watap Lake	Cook	MN	210 ft	1,993 acres	NR	9 ft
8	Sagamore Mine Lake	Crow Wing	MN	210 ft	119 acres	NR	23.8 ft
9	Gabimichigami Lake	Cook	MN	209 ft	1,186 acres	NR	11.5 ft
10	Ten Mile Lake	Cass	MN	208 ft	5,080 acres	A	20.5 ft
11	Loon Lake	Cook	MN	202 ft	1,095 acres	A	17.4 ft
12	Gunflint Lake	Cook	MN	200 ft	4,009 acres	A	16.5 ft
13	Strup Lake	Lake	MN	195 ft	1,689 acres	NR	10 ft
14	Sand Point Lake	St. Louis	MN	184 ft	8,527 acres	NR	6.6 ft
15	Larson Lake	Itasca	MN	177 ft	208 acres	B	21 ft
16	Lac la Croix Lake	St. Louis	MN	168 ft	29,597 acres	NR	8 ft
17	Crooked Lake	Lake	MN	165 ft	10,360 acres	NR	9 ft
18	Carlos Lake	Douglas	MN	163 ft	2,605 acres	A	18 ft
19	Rainy Lake	Koochiching	MN	161 ft	210,200 acres	NR	7.5 ft
20	Trout Lake	Itasca	MN	157 ft	1,743 acres	A	18 ft
21	Caribou Lake	Itasca	MN	152 ft	247 acres	NR	31 ft
22	Little Saganaga Lake	Cook	MN	150 ft	1,627 acres	NR	7 ft
23	Snowbank Lake	Lake	MN	150 ft	4,655 acres	B	15.1 ft
24	Steamboat Bay Lake	Cass	MN	150 ft	103,444 acres	A	9.8 ft
25	Six Lake	Otter Tail	MN	140 ft	197 acres	A	21 ft
26	Elmo Lake	Washington	MN	140 ft	257 acres	A	11.1 ft
27	South Lake	Cook	MN	140 ft	1,145 acres	NR	26 ft
28	Miner'S Pit West Lake	St. Louis	MN	140 ft	141 acres	NR	23.1 ft
29	Whitefish Lake	Crow Wing	MN	138 ft	7,714 acres	A	14.4 ft
30	Rose Lake	Otter Tail	MN	137 ft	1,200 acres	NR	16 ft
31	Long Lake	Hubbard	MN	135 ft	1,926 acres	A	11.2 ft
32	Big Sand Lake	Hubbard	MN	135 ft	1,639 acres	A	23 ft
33	Geneva Lake	Walworth	WI	135 ft	5,401 acres	A	21 ft
34	Kabekona Lake	Hubbard	MN	133 ft	2,433 acres	A	12.1 ft
35	Koronis Lake	Stearns	MN	132 ft	2,968 acres	C	6 ft
36	Duncan Lake	Cook	MN	130 ft	477 acres	NR	21.5 ft
37	Kekekabic Lake	Lake	MN	130 ft	55 acres	NR	19 ft
38	Oyster Lake	St. Louis	MN	130 ft	763 acres	NR	6.6 ft
39	Mountain Lake	Unknown	MN	130 ft	1,344 acres	NR	19 ft
40	Rove Lake	Cook	MN	130 ft	1,344 acres	NR	9 ft
41	Roosevelt Lake	Cass	MN	129 ft	1,511 acres	A	11.1 ft
42	Long Lake	Otter Tail	MN	128 ft	1,289 acres	A	12.3 ft
43	Big Trout Lake	Crow Wing	MN	128 ft	1,366 acres	A	16.9 ft
44	Burntside Lake	St. Louis	MN	126 ft	7,314 acres	A	16 ft
45	Round Lake	Aitkin	MN	125 ft	737 acres	A	14.5 ft
46	Jasper Lake	Cook	MN	125 ft	246 acres	NR	12 ft
47	Mina Lake	Douglas	MN	123 ft	411 acres	NR	16 ft
48	Big Watab Lake	Stearns	MN	123 ft	246 acres	NR	20.5 ft
49	Deer Lake	Itasca	MN	121 ft	4,093 acres	A	13.1 ft
50	Bluewater Lake	Itasca	MN	120 ft	364 acres	A	18.5 ft

Where to stay near the deepest lakes

Planning a trip to Minnesota or Wisconsin's deepest lakes? Jump to live cabin and hotel availability on each lake's page.

Frequently Asked Questions

Gilbert Pit Lake in St. Louis County, MN, is the deepest on our index at a maximum depth of 443 ft.

Maximum depth comes from state DNR bathymetric (depth-contour) surveys, which sound the lake bottom on a grid and record the deepest point. We report the official maximum depth from the most recent published survey. Some of the very deepest entries are flooded mine pits, which reach extreme depths in a small footprint.

Deep lakes stratify in summer: a warm surface layer floats on a cold bottom layer, and the two do not mix. That traps phosphorus released from bottom sediments down low, away from the sunlit surface where it would otherwise fuel algae. Deep lakes also have more water volume to dilute nutrient inputs, so they tend to stay clearer than shallow lakes of the same area.

Depth helps cold-water species. Lake trout, cisco, and whitefish need the cold, oxygen-rich water that only deep, stratified lakes hold through summer. Walleye and bass do well in lakes with a mix of deep basins and shallow structure. Very deep mine-pit lakes can be clear but biologically sparse, with limited shallow habitat.

Cleanest Lakes →Clearest Water →Largest Lakes →Worst Water Quality →Best Fishing →

More on depth and water quality

Deepest Lakes in America We Grade — and How Clean They Are

The deepest lakes we grade, ranked by maximum depth with their water-quality grades alongside. Depth helps on average — it does not decide the letter.

Do Deeper Lakes Have Better Water Quality?

Surveyed maximum depth against A–F nutrient-and-algae grades: the pattern, the shallow lakes that still grade an A, and why land use beats bathymetry.

Are Reservoirs Cleaner Than Natural Lakes?

Dam-built reservoirs and natural lakes graded side by side on the same nutrient and algae measurements — the gap, the reasons behind it, and the exceptions.

Water Clarity Explained: What Secchi Depth Tells You

What a Secchi depth reading measures, how many feet counts as good clarity, and why clear water is not always clean — with readings from graded lakes.

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