Unit 18, Idaho

Elevation ranges from roughly 2,000 feet along the Snake River canyon floor to 9,420 feet at the He Devil peak in the Seven Devils Mountains. The terrain is extremely rugged — steep-walled canyon country forming one of the deepest river gorges in North America — transitioning to high alpine ridges. Sheer cliffs, rocky slopes, and narrow drainages severely limit vehicle and foot access. Above 8,500 feet, terrain is open and rocky with scattered pines, firs, and shrubs.

US Highway 95 borders the eastern boundary and passes through Riggins. Forest Road 517 (Seven Devils Road) departs US-95 just south of Riggins and climbs to Windy Saddle — recommended for high-clearance vehicles only, not suitable for RVs or trailers. Forest Road 112 continues to Black Lake Campground and requires high-clearance 4WD. Highway District Road 493 connects US-95 near White Bird to Pittsburg Landing — a 19-20 mile single-lane steep gravel road suitable for passenger cars with care. The Hells Canyon Wilderness (56,535 acres, 31.27% of the unit) prohibits all motorized vehicles including ATVs and mountain bikes. ATVs are permitted on designated main forest roads outside wilderness only. Most quality elk and deer hunting occurs along and below Trail 101 (Boise Trail) near the wilderness boundary on the east side of the Seven Devils. Access to the canyon bottom and wilderness interior requires backpacking or horseback travel. 4WD is strongly advisable in fall due to steep terrain and adverse weather.

Below approximately 3,500 feet, forests dominate north- and east-facing slopes while south- and west-facing slopes support grass and brush communities. Common tree species include ponderosa pine, Douglas fir, western larch, Engelmann spruce, and subalpine fir. Above the forested zone, vegetation transitions to open, rocky alpine communities. The unit is 71% forested and 28% rangeland/grass-brush, with riparian corridors along the Snake and Salmon Rivers at lower elevations.

Unit 18 supports mule deer as the primary big game species and is described by IDFG as one of the better Idaho units for mature mule deer. White-tailed deer are present in small numbers and a few are harvested annually. Elk inhabit the unit though populations in the Hells Canyon Elk Zone (Units 11, 13, 18) are described by IDFG as relatively low compared to other Idaho regions. Rocky Mountain bighorn sheep occupy the Hells Canyon corridor, with the Hells Canyon herd recovering from respiratory disease (Movi/pneumonia) in recent years with improved lamb survival and recruitment. Rocky Mountain goats are present in the Seven Devils Mountains. Black bears are present year-round on forested slopes. Mountain lions are resident throughout. Gray wolves are present. Upland birds include chukar partridge, forest grouse, turkey, quail, pheasant, and Hungarian partridge. The Snake and Salmon Rivers support steelhead, chinook salmon, and sturgeon. Deer in this unit are within the CWD Management Zone — CWD was detected in nearby units and spreading as of 2025; mandatory CWD testing is required within 10 days of harvest and carcass transport restrictions apply.