Salmon–Challis National Forest spans 4,235,940 acres in east-central Idaho, making it one of the largest national forests in the contiguous United States. Formed from the historic Salmon and Challis national forests, it covers rugged mountains and deep river canyons, with headquarters in Salmon and ranger districts across both sections. The forest includes most of the Frank Church–River of No Return Wilderness, most of the Jim McClure–Jerry Peak Wilderness, and part of the Sawtooth Wilderness. It also contains major Idaho landmarks, including Borah Peak, the Salmon River, and the headwaters of the Big Lost River, and is prized for its vast, remote mountain backcountry.