Boise National Forest is a National Forest covering 2,203,703 acres of the U.S. state of Idaho. Created on July 1, 1908, from part of Sawtooth National Forest, it is managed by the U.S. Forest Service as five units: the Cascade, Emmett, Idaho City, Lowman, and Mountain Home ranger districts. The Idaho Batholith underlies most of Boise National Forest, forming the forest's Boise, Salmon River, and West mountain ranges; the forest reaches a maximum elevation of 9,730 feet on Steel Mountain.