Salmon–Challis National Forest is located in east central sections of the U.S. state of Idaho. At 4,235,940 acres (6,618.66 sq mi, or 17,142.24 km2) it is one of the largest national forests in the lower 48 states and also has most of the land area of the Frank Church–River of No Return Wilderness, which is the largest wilderness area south of Alaska. The combined forest headquarters are located in Salmon, Idaho.