Unit 40, Idaho

The unit spans roughly 1,447,543 acres with elevations ranging from approximately 2,600 feet along the Snake River plain to about 8,400 feet at high peaks including South Mountain, War Eagle Mountain, Florida Mountain, and Hayden Peak in the Owyhee Mountains. Lower terrain consists of open desert flats, shallow canyon drainages, and rolling sagebrush hills. Mid-elevation features juniper-covered ridges and rocky escarpments. The North Fork of the Owyhee River cuts deep canyon terrain in the southern portion. The unit has rugged, isolated backcountry without the extremely vertical canyon systems found farther south.

The entire unit falls under the BLM Owyhee Field Office jurisdiction (101 S. Bruneau Hwy, Marsing, ID 83639; 208-896-5912) — there is no National Forest land within Unit 40. BLM manages approximately 65.5% of the unit; private land is 24%; State of Idaho 9.9%; Bureau of Reclamation ~0.45%. Key access corridors: State Highway 78 forms the northern boundary from Grandview west toward the Oregon line; State Highway 51 runs north-south through the eastern portion. The Owyhee Uplands Backcountry Scenic Byway (Mud Flat Road / Poison Creek Road system) is the primary interior access route connecting SH-78 south through the heart of the unit toward Silver City and the Oregon border — high-clearance required. The Silver City Road leads from Murphy, ID into the historic mining district; a free primitive BLM campground is at Silver City. The North Fork Owyhee Wilderness (44,684 acres, 3.09% of the unit) prohibits motorized vehicles. The Jump Creek Recreation Site (BLM) near Marsing provides northern entry. Rough two-track roads throughout the BLM lands require high-clearance 4WD.

Dominant vegetation shifts by elevation. Lower bajadas and broad flats support sagebrush (big and Wyoming), greasewood, rabbitbrush, and prickly pear cactus — classic high-desert steppe. Mid-elevation slopes transition into western juniper woodlands with mountain mahogany and serviceberry. Higher ridges and mountain tops in the Owyhee Mountains hold ponderosa pine and mixed conifer (pine-fir) stands. Riparian corridors along the Owyhee River drainages, Jump Creek, and other seasonal streams support cottonwood, willow, and dense brush. The northern edge grades into irrigated farmland and hayland along the Snake River plain. Rangeland constitutes approximately 73% of the unit; forest cover approximately 16%; irrigated agricultural land approximately 9%; riparian roughly 1.6%.

Unit 40 supports mule deer as the primary big-game species. Rocky Mountain elk are present and managed through controlled hunts only in the Owyhee Zone. Pronghorn antelope occupy open sagebrush and desert flats across the unit and the broader 40/41/42 Zone. California bighorn sheep have an established population in the Owyhee Mountains. Mountain lion and gray wolf are present with active hunting seasons. Upland birds include chukar partridge (particularly along rocky rimrock and canyon edges), sage-grouse, sharp-tailed grouse, quail, and pheasant along the agricultural northern fringe. Waterfowl use riparian corridors and the Snake River border. Wild horses are managed in several BLM herd management areas within the unit. White-tailed deer exist but are a small, incidental component; mule deer dominate harvest.