Lakes / Montana / Rock Island Lake
Rock Island Lake, Montana
156 acres
Surface Area
About 100 ft
Max Depth (Approximate)
8,177.04 ft
Surface Elevation
Where It Sits, and How Deep It Goes
Locator - Montana
45.02 degrees N, 109.81 degrees W - Park County. State and county outlines drawn from Census boundary data; the lake marker is placed by its Montana Fish, Wildlife & Parks coordinates, not by eye. Schematic - not a survey map.
Depth Profile - Rock Island Lake
Schematic cross-section drawn to one shared depth scale - not a survey or bathymetric map. Max depth is approximate, from state bathymetry.
How Rock Island Lake Stacks Up
- About 75 miles from Bozeman, as the crow flies.
- 2 fish species on the FWP list for this lake.
Fish Species
Brook TroutYellowstone Cutthroat Trout
Species recorded for this lake. Presence only - no abundance ratings.
Facts and Figures
Waterbody ID56787713
CountyPark
Coordinates45.0156, -109.8099
Largest Lakes in Montana
| # | Lake | County | Surface Area | Max Depth |
|---|---|---|---|---|
| 1 | Fort Peck Lake | Valley | 233,053 acres | - |
| 2 | Flathead Lake | Lake | 122,132 acres | About 380 ft |
| 3 | Canyon Ferry Lake | Broadwater | 32,773 acres | About 170 ft |
| 4 | Lake Koocanusa | Lincoln | 28,723 acres | - |
| 5 | Hungry Horse Reservoir | Flathead | 23,577 acres | - |
Sources: Montana Fish, Wildlife & Parks lake data (ID 56787713); Washington Dept. of Ecology bathymetry (approximate max depth). Verified October 30, 2026.