Unit 20, Idaho

Unit 20 covers approximately 303,000 acres with elevations ranging from roughly 1,965 feet along the Salmon River canyon bottom to 8,400 feet on the highest peaks and ridges. The unit is characterized by deep river canyons, steep slopes, long ridges, and high rocky peaks concentrated in the central and eastern portions. The Salmon River forms part of the unit's southern boundary. High-elevation ridges are rocky and largely open, while lower terrain is heavily forested.

Unit 20 is 99.38% U.S. Forest Service land (Nez Perce-Clearwater National Forest). The Frank Church-River of No Return Wilderness comprises 188,064 acres (62.07%) of the unit; the Selway-Bitterroot Wilderness adds approximately 629 acres (0.21%). No motorized vehicles are permitted within wilderness boundaries. Primary motorized access to the unit perimeter is via Forest Road 468 (the Magruder Corridor Road), a historic 101-mile single-lane unimproved route running east-west between Red River Road #222 (65 miles east of Grangeville via Highway 14) and the Montana border near Darby, Montana — between the Selway-Bitterroot Wilderness to the north and the Frank Church Wilderness to the south. The road is suitable only for high-clearance vehicles; travel averages 12–15 mph and takes 6–8 hours end to end. The Corn Creek Trailhead on the Salmon River provides foot and stock access to the southern portion. The Selway River Road (FR 223) and Wilderness Gateway Campground on State Highway 12 provide northern access. Float trips on the Salmon River (with required permits) can reach southern trailheads. Deep wilderness access requires backpacking or pack stock. Seasonal closures affect portions of FR 468 and side roads in winter and early spring.

The unit is nearly 100% forested. Lower-elevation slopes and canyon walls feature ponderosa pine and mixed conifer stands. Mid-elevation terrain is dominated by lodgepole pine, Douglas-fir, and Engelmann spruce. South-facing slopes above the Salmon River are grassy and rocky with brush in draws. Bear grass covers much of the forest floor at mid to upper elevations. Old burns and historically logged areas support dense brush, young saplings, wildflowers, and forbs that create important edge habitat. Rockslide chutes and avalanche paths add structural diversity. Meadows with native grasses and forbs occur at higher elevations.

Unit 20 supports mule deer and white-tailed deer (approximately 57% mule deer and 42% whitetail of 2025 harvest), Rocky Mountain elk, black bear, mountain lion, gray wolf, moose, and Rocky Mountain bighorn sheep. Wolves have had a documented negative impact on elk herds in the Selway Zone, with IDFG reporting that elk numbers and harvest remain relatively low; improved calf recruitment in recent years offers a more optimistic outlook. Elk move seasonally — summer range on high ridges and alpine meadows, transitioning to lower canyon and mid-elevation forested slopes as snow accumulates. Deer favor edges created by old burns, avalanche chutes, and brush fields. Bighorn sheep occupy rocky canyon terrain and high open ridges. Moose are present at low densities. The Salmon River corridor provides important habitat connectivity and supports steelhead and native trout fisheries.