GMU 45B Unit 45B — Yuma
The Kofa heart: King Valley, the Castle Domes, and big desert bucks for the patient glasser
Southwestern Arizona low desert — Kofa National Wildlife Refuge · Last reviewed 2026-07-12
Area
418
sq mi
Public land
100%
approx.
Elevation
900–4,877
feet
Motorized
limited
access
Overview
Unit 45B lies entirely within the Kofa National Wildlife Refuge and includes some of Arizona's best-known desert-bighorn and desert mule deer country. Much of the unit is designated wilderness with special vehicle rules. Deer habitat runs from flat-to-rolling low desert — hard to hunt even in good years — to the rugged interior Kofa Mountains and the Castle Dome Mountains, where canyon bottoms and washes around the range edges produce the largest bucks. It is a scouting-and-glassing unit rewarding those who put in the miles.
Terrain
Low desert flats and King Valley rising into the steep Kofa and Castle Dome ranges; sheer cliffs and short, severe elevation changes in the mountains.
Cover: Creosote-bursage flats and paloverde–ironwood–saguaro bajadas, with heavier vegetation in canyon bottoms and washes along the range edges.
Landmarks: Kofa Mountains · Castle Dome Mountains · King Valley · Kofa Wilderness · Kofa National Wildlife Refuge
Access
All of Unit 45B lies within the Kofa National Wildlife Refuge, and much of it is wilderness with special regulations: vehicle use is limited to existing designated roads and must remain within 100 feet of those roads. Hunting is permitted on the refuge. No tribal land in this unit.
Managers: Kofa National Wildlife Refuge (USFWS), Wilderness
Access points: El Paso Natural Gas Line Road (about 8 miles south of Quartzsite off Highway 95) into the interior Kofa Mountains · Roads accessing King Valley and the Castle Dome edges
Species notes
Bighorn Sheep
common trophyPremier Kofa desert-bighorn range with a long history of quality rams. Rocky terrain and sheer cliffs make for physically demanding sheep hunting, with elevation varying greatly over short distances. Tags are coveted and draw-only.
- →Glass steep faces and rimrock in the Kofa and Castle Dome ranges at first and last light
- →Plan foot routes off designated roads into wilderness
- →Locate water and shade pockets that concentrate sheep in heat
Mule Deer
common qualityPart of the quality 45A/B/C combined unit. Much of the habitat is flat-to-rolling low desert that hunts hard, but the interior Kofa high country historically held the best densities, and the canyon bottoms and washes around the Castle Domes and King Valley produce large bucks.
- →Glass King Valley from surrounding hills and high points
- →Work the canyon bottoms and washes at the edges of the Castle Dome Mountains for big bucks
- →Push into the interior Kofa high country where deer are most concentrated
Pro tips
- →Hunt King Valley by finding hills and glassing the flats — big, wary bucks live there
- →Work the Castle Dome edges: few deer in the peaks, but the canyon mouths hold trophies
- →Stay within 100 feet of designated roads when driving in refuge wilderness
- →Give yourself multiple scouting days — the best deer are deep and dispersed
- →Pack all water and self-recovery gear; the refuge has no services
Watch out for
- !Entire unit is Kofa NWR wilderness/refuge — vehicles restricted to designated roads, within 100 ft
- !No water, fuel, or services on the refuge
- !Steep, cliffy sheep terrain with real fall risk
- !Extreme desert heat on early hunts
- !Flat low-desert deer habitat hunts hard even in good years — manage expectations
Logistics
Quartzsite (roughly 8 miles north of the refuge on Highway 95) is the last dependable fuel and supply point. There is no water or services inside the refuge — carry all your own, run high-clearance, and budget scouting days. Camp only along designated roads per refuge rules.
Nearest towns: Quartzsite, Yuma
Seasons & regulations
This page carries no season dates or regulations. Get current rules from the official Arizona sources:
Research sources: AZGFD — Unit 45A/45B (Kofa) · Kofa NWR Public Use and Hunting Regulations (USFWS) · GOHUNT — Arizona Unit 45B Profile
FAQ
- How big is GMU 45B in Arizona?
- GMU 45B (Unit 45B — Yuma) covers about 418 square miles, ranging from roughly 900 to 4,877 feet in elevation. Area is computed from the unit boundary polygon.
- How much public land is in GMU 45B?
- Approximately 100% of the unit is public land. Primary managers: Kofa National Wildlife Refuge (USFWS), Wilderness. Always verify ownership boundaries on the ground.
- What species does the catalog list for GMU 45B?
- Bighorn Sheep, Mule Deer. For seasons, tags, and regulations, use the official Arizona agency resources linked on this page — this page carries no regulatory information.
Put GMU 45B on your map.
Boundary lines, public/private ownership, topo, and offline maps for this unit — in Baseline Maps, free for 14 days.