Lakes / Idaho / Washington County / Buttermilk Slough
Buttermilk Slough, Idaho
59.8 acres
Surface Area
Where It Sits, and How Deep It Goes
Locator - Idaho
44.19 degrees N, 116.90 degrees W - Washington 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 Buttermilk Slough Stacks Up
- Larger than 42% of the 316 lakes counted in Idaho.
- About 53 miles from Boise, as the crow flies.
Lakes Nearby
| Lake | County | Distance | Surface Area |
|---|---|---|---|
| Barton Reservoir | Washington | 9.1 mi | 56.09 acres |
| Mann Creek Reservoir | Washington | 14 mi | 230.3 acres |
| Paddock Valley Reservoir | Washington | 15 mi | 1,182.15 acres |
| Soulen Reservoir | Washington | 17 mi | 91.43 acres |
| Little Crane Creek Reservoir | Washington | 17 mi | 35.58 acres |
| Fairchild Reservoir | Washington | 19 mi | 96.62 acres |
Straight-line distance between lake centers.
Facts and Figures
Questions About Buttermilk Slough
How Big Is Buttermilk Slough?
Buttermilk Slough covers 59.8 acres in Washington County, Idaho.
What Is the Largest Lake in Washington County?
Brownlee Reservoir is the largest lake in Washington County, at 12,535.1 acres.
Largest Lakes in Idaho
| # | Lake | County | Surface Area | Max Depth |
|---|---|---|---|---|
| 1 | Lake Pend Oreille | Bonner | 92,764.44 acres | - |
| 2 | American Falls Reservoir | Power | 55,319.78 acres | - |
| 3 | Coeur d'Alene Lake | Kootenai | 26,891.64 acres | - |
| 4 | Lake Cascade | Valley | 25,043.4 acres | - |
| 5 | Priest Lake | Bonner | 23,425.59 acres | - |
All 316 Idaho lakes ranked by surface area
Sources: USGS National Hydrography Dataset (The National Map) lake data (ID 133112832). Verified October 30, 2026.