| Reas Pass | |
| Elevation Ft: | 6930 |
| Elevation Ref: | [1] |
| Traversed: | former Union Pacific Railroad right-of-way |
| Location: | Fremont County, Idaho, US |
| Range: | Rocky Mountains |
| Coordinates: | 44.5675°N -111.1894°W |
| Topo: | USGS Reas Pass |
Reas Pass, elevation 6930feet, is a mountain pass on the Continental Divide in Fremont County, Idaho, about 8miles southwest of West Yellowstone, Montana. The pass lies essentially on the Idaho-Montana border, but modern maps[1] show that the summit lies entirely in Idaho, because the Divide and the state line do not quite coincide here. The pass is also somewhat unusual in that, despite being the lowest crossing of the Divide in the vicinity, it has evidently never been traversed by a highway of any significance.[2] Starting in 1909, it was used by a branch line of the Union Pacific Railroad running between Ashton, Idaho and West Yellowstone; however, the line eventually became unprofitable and was closed in 1979.[3]