Bitterroot National Forest comprises 1.587 million acres (6,423 km2) in west-central Montana and eastern Idaho of the United States.

[1] Founded in 1898, the forest is located in the Bitterroot and Sapphire Mountains with elevations ranging from 2,200 feet (650 m) along the Salmon River in Idaho to 10,157 foot (3,100 m) Trapper Peak.

Heavy logging and other resource depletion beginning in the 1880s led conservationists to push for the preservation of the forest.

[2] The Bitter Root Forest Reserve was established by the United States General Land Office on March 1, 1898, with 4,147,200 acres (16,783 km2).

Other lands were transferred from Bitterroot to Beaverhead, Clearwater, Nez Perce and Salmon National Forests.

Grazing rights are leased to private landowners in the lower altitudes where grasses and shrublands are dominant.

The Allan Mountain area is a lower-elevation part of the Bitterroot Range that features extensive coniferous forests, steep canyons, and pockets of old-growth ponderosa pine and Douglas-fir.

Within the area is Overwhich Falls, a popular attraction; hiker's gentian (Gentianopsis simplex) and primrose monkey flower (mimulus primuloides), sensitive plants, are found here in wet meadows.