Reas Pass, elevation , is a mountain pass on the

Continental Divide A continental divide is a drainage divide on a continent such that the drainage basin on one side of the divide feeds into one ocean or sea, and the basin on the other side either feeds into a different ocean or sea, or else is endorheic, not ...

in Fremont County, Idaho, about southwest of

West Yellowstone, Montana West Yellowstone is a town in Gallatin County, Montana, United States, adjacent to Yellowstone National Park. The population was 1,272 at the 2020 census. West Yellowstone is served by Yellowstone Airport. It is part of the Bozeman, MT Microp ...

. The pass lies essentially on the Idaho-Montana border, but modern maps 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. 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.

References

Landforms of Fremont County, Idaho Rail mountain passes of the United States Mountain passes of Idaho {{FremontCountyID-geo-stub