The Selway-Bitterroot Wilderness Area consists of 1,340,460 acres straddling the Bitterroot Range that is the border between Idaho and Montana. Eighty percent of the wilderness is on the Idaho side. Terrain is rugged steep mountains and deep canyons. Elevations range from near 550 m (1,800 ft) on the Selway and Lochsa Rivers to 3,097 m (10,157 ft) at the summit of Trapper Peak.

This northern Idaho/western Montana Wilderness area is remote from any major source regions. The nearest population center is Missoula Montana located 100 km north. The major industry in the region is timber. Data comparing the best and worst visibility days in the Selway Bitterroot Wilderness show poor visibility most often occurs in summer months, due to higher levels of organic matter attributed to regional wildfires.