Lakes / South Dakota / Dewey County / Lake Oahe
Lake Oahe, South Dakota
309,912.57 acres
Surface Area
Where It Sits, and How Deep It Goes
Locator - South Dakota
44.79 degrees N, 100.57 degrees W - Dewey County. State and county outlines drawn from Census boundary data; the lake marker is placed by its USGS National Hydrography Dataset coordinates, not by eye. Schematic - not a survey map.
How Lake Oahe Stacks Up
- The largest lake counted in South Dakota by surface area - 309,912.57 acres.
- The largest lake in Dewey County among those counted.
- About 31 miles from Pierre, as the crow flies.
Lakes Nearby
| Lake | County | Distance | Surface Area |
|---|---|---|---|
| Fuller Lake | Sully | 7.8 mi | 27.68 acres |
| Lake Okobojo | Sully | 13 mi | 91.68 acres |
| Sully Lake | Sully | 20 mi | 212.26 acres |
| Warnes Slough | Sully | 21 mi | 364.97 acres |
| Lake Hurley | Potter | 29 mi | 106.01 acres |
| Goose Creek Dam | Dewey | 31 mi | 44.23 acres |
Straight-line distance between lake centers.
Facts and Figures
Questions About Lake Oahe
How Big Is Lake Oahe?
Lake Oahe covers 309,912.57 acres in Dewey County, South Dakota.
What Is the Largest Lake in Dewey County?
Lake Oahe is the largest lake in Dewey County, at 309,912.57 acres.
Largest Lakes in South Dakota
| # | Lake | County | Surface Area | Max Depth |
|---|---|---|---|---|
| 1 | Lake Oahe | Dewey | 309,912.57 acres | - |
| 2 | Lake Francis Case | Charles Mix | 82,166.92 acres | - |
| 3 | Lake Sharpe | Hughes | 58,419.67 acres | - |
| 4 | Lewis and Clark Lake | Bon Homme | 25,141.99 acres | - |
| 5 | Lake Thompson | Kingsbury | 13,887.93 acres | - |
All 533 South Dakota lakes ranked by surface area
Sources: USGS National Hydrography Dataset (The National Map) lake data (ID 139478686). Verified October 30, 2026.