Two canoes crossing open water between forested points in the Boundary Waters

Updated August 2026

Biggest Lake in South Dakota: Lake Francis Case (102,000 acres)

Lake Francis Case is South Dakota's largest inland lake per the South Dakota Game, Fish and Parks. Below: 50 South Dakota lakes ranked by surface area.

The largest lake in South Dakota is Lake Francis Case at 102,000 acres , in Hughes, Stanley, Sully, Potter, Walworth, Campbell, Corson, Dewey County, according to the South Dakota Game, Fish and Parks. Lake Oahe is larger at 370,000 acres. It is a Missouri River reservoir shared with North Dakota, so it is not a lake lying entirely within South Dakota.

Lake Francis Case isn't in our water-quality index — we grade lakes with enough EPA Water Quality Portal samples to score, which leaves out many large reservoirs and border waters. The ranking below covers the 50 South Dakota lakes we do grade, led by Dry Lake Number Two.

Source: South Dakota Game, Fish and Parks (2026-07-30). The table below ranks the South Dakota lakes in our own index by surface area.

Lakes with area data

6,442

Largest (acres)

999

Median of top 50

0/50

Reservoirs (vs natural)

Reading South Dakota's size profile

South Dakota's largest lake by surface area is Dry Lake Number Two in Clark County, spanning 6,442 acres. Most of South Dakota's biggest waters are natural basins left by glaciers, with stable shorelines and deep main basins.

Surface area is a poor proxy for water quality on its own — a large lake can hold a clean, deep core and a nutrient-loaded bay at the same time. Each lake below links to its full report card with grade, clarity, depth, and EPA impairment status. Area figures come from state DNR surveys and the USACE National Inventory of Dams; grades come from EPA and state monitoring data.

The 50 biggest lakes in South Dakota by surface area

#	Lake	County	Surface area	Max depth	Grade
1	Dry Lake Number Two	Clark	6,442 acres	-	NR
2	Columbia Road Reservoir	Brown	4,224 acres	-	NR
3	Lake Marsh	Hamlin	3,026 acres	-	NR
4	Long Lake	Codington	2,489 acres	-	NR
5	Swan Lake	Walworth	2,467 acres	-	NR
6	Dry Lake Number One	Clark	2,461 acres	-	NR
7	South Waubay Lake	Day	2,335 acres	-	NR
8	Long Lake	Day	2,062 acres	-	NR
9	Buffalo Lakes	Marshall	1,986 acres	-	NR
10	Goose Lake	Codington	1,948 acres	-	NR
11	Lake Sinai	Brookings	1,790 acres	-	NR
12	White Lake	Aurora	1,684 acres	-	NR
13	Opitz Lake	Marshall	1,664 acres	-	NR
14	Grass Lake	Codington	1,610 acres	-	NR
15	Parsons Pass	Marshall	1,583 acres	-	NR
16	Goose Lake	Day	1,483 acres	-	NR
17	Rush Lake	Day	1,463 acres	-	NR
18	Lake Pocasse	Campbell	1,371 acres	-	NR
19	Solomon Slough	Day	1,290 acres	-	NR
20	Clear Lake	Marshall	1,199 acres	-	NR
21	Piyas Lake	Marshall	1,155 acres	-	NR
22	Green Lake	Potter	1,153 acres	-	NR
23	Spirit Lake	Kingsbury	1,066 acres	-	NR
24	Drywood Lakes	Roberts	1,027 acres	-	NR
25	Stone Lake	Sully	1,024 acres	-	NR
26	Twin Lakes	Spink	999 acres	-	NR
27	Spring Lake	Day	984 acres	-	NR
28	Platte Lake	Aurora	966 acres	-	NR
29	Lake Nicholson	Codington	947 acres	-	NR
30	Swan Lake	Clark	936 acres	-	NR
31	North Scatterwood Lake	Edmunds	932 acres	-	NR
32	Round Lake	Deuel	931 acres	-	NR
33	South Scatterwood Lake	Faulk	727 acres	-	NR
34	Clear Lake	Hamlin	706 acres	-	NR
35	Wigdale Lake	Deuel	692 acres	-	NR
36	Lewis and Clark Lake	Bon Homme	691 acres	-	NR
37	Sumner Slough	Codington	682 acres	-	NR
38	Spring Lake	Walworth	678 acres	-	NR
39	Horseshoe Lake	Codington	643 acres	-	NR
40	Campbell Slough	Day	638 acres	-	NR
41	Baxter Slough	Hamlin	637 acres	-	NR
42	South Red Iron Lake	Marshall	624 acres	-	NR
43	Wolf Slough	Codington	620 acres	-	NR
44	Minnewasta Lake	Day	610 acres	-	NR
45	Horseshoe Lake	Day	607 acres	-	NR
46	Cottonwood Lake	Roberts	597 acres	-	NR
47	Cottonwood Lake	Codington	595 acres	-	NR
48	Flight Lake	Potter	582 acres	-	NR
49	Horse Shoe Lake	Aurora	580 acres	-	NR
50	Antelope Lake	Day	574 acres	-	NR

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Frequently Asked Questions

What is the largest lake in South Dakota?

Lake Francis Case, at 102,000 acres, in Hughes, Stanley, Sully, Potter, Walworth, Campbell, Corson, Dewey County. Lake Oahe is larger at 370,000 acres. It is a Missouri River reservoir shared with North Dakota, so it is not a lake lying entirely within South Dakota. Source: South Dakota Game, Fish and Parks, 2026-07-30.

How is lake surface area measured?

Surface area comes from state DNR lake surveys and, for reservoirs, US Army Corps of Engineers (USACE) National Inventory of Dams records. Area is reported in acres at normal pool level. Reservoirs rise and fall with management and drought, so their listed area is the long-term normal rather than a single-day reading.

Are South Dakota's largest lakes natural or reservoirs?

Of the top 50 South Dakota lakes by area, 0 sit on a dammed river (reservoirs) and 50 are natural basins. Glacial states (MN, WI, MI, NY) skew natural; plains and southern states (MO, IA, ND, OH) skew toward reservoirs built for water supply, flood control, and recreation.

Do larger lakes have better water quality?

Not reliably. Quality varies more within a big lake than between lakes — a large lake can have a clean, deep main basin and a murky, algae-prone bay fed by a tributary, so one grade can mask wide swings. Depth, watershed land use, and how fast the lake flushes matter far more than raw surface area.

How big is the typical South Dakota lake in this ranking?

Across the top 50 South Dakota lakes by surface area, the median is 999 acres (Twin Lakes). This list is biased toward the biggest waters; the typical South Dakota lake is far smaller.

Where to stay near South Dakota's largest lakes

Planning a trip? Jump to live cabin, resort, and hotel availability near South Dakota's biggest lakes.

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