Bitterroot Range, part of the Rocky Mts., forms most of Idaho-Mont. state line; extends from Snake R. Plain in S NNW to L. Pend Oreille. S part, N to Lost Trail Pass (7,014 ft/2,138 m), forms Continental Divide and is also called Beaverhead Mts. N part of the range forms border bet. Pacific (W) and Mountain (E) time zones. The main range, running NW-SE, includes Trapper Peak (10,157 ft/3,096 m). Mt. Ajax, Idaho (10,900 ft/3,322 m), in an E-running spur to the S, is the highest peak. Salmon and Clearwater drainage basins to W, Missouri and Clarks Fork drainage basins to E. Discovered in the 1804–1805 expedition of Lewis and Clark, the rugged mt. range has long been one of the most impenetrable in the U.S.; except for its foothills, it remains almost completely unexploited.
