Unit 390

The Big Belt Mountains form the eastern skyline with Grassy Mountain and Boulder Mountain serving as prominent reference points for orientation. Windy Ridge offers glassing vantage points overlooking the lower valleys. Cave Bay and Canyon Ferry Reservoir anchor the western boundary—critical landmarks visible from most ridges.

Major creek drainages including Cottonwood Creek, Clear Creek, and Sixteenmile Creek provide natural travel corridors and navigation aids. Franklin Spring and other scattered springs mark reliable water sources on the ridges and benches.

Terrain ranges from low reservoir basins near 3,800 feet to rocky peaks above 9,400 feet. Most hunting occurs in the 5,000-7,000 foot zone where sagebrush flats and rolling foothills dominate. Timber increases with elevation, shifting from scattered ponderosa and juniper on lower slopes to denser conifer stands on the Big Belt Mountains.

Open grassland benches provide excellent sightlines across valley floors. Vegetation varies seasonally with spring growth in bottomlands and persistent sagebrush across mid-elevation benches throughout the year.

Over 830 miles of roads traverse the unit but much consists of ranch and irrigation access rather than hunter-friendly routes. Fair connectivity means concentrated hunting pressure likely follows the better road access points while significant terrain remains lightly hunted. Several small communities rim the unit—Townsend, Toston, Diamond City—providing supply options.

Irrigated valley lands mixed through the unit create access complications and boundaries to respect. The combination of rolling topography, moderate forest, and fair roads means hunters must work to find quiet country but opportunity exists for those willing to venture beyond roadside parking.

Unit 390 occupies the rolling terrain between Canyon Ferry Reservoir and the Big Belt Mountains, spanning portions of Broadwater, Lewis and Clark, and Gallatin Counties. The western boundary traces Cave Bay northward up Cave Gulch to Hedges Mountain, then follows the Trout Creek-Magpie Creek Divide eastward. The northern edge runs along county lines before dropping south along Sixteenmile Creek to the Missouri River, then follows the reservoir shoreline and river back to the starting point.

The unit encompasses foothill country transitioning from valley floor to mountain slopes.

Canyon Ferry Reservoir dominates the western boundary as a perennial water source but lies at the unit edge for most hunters. Sixteenmile Creek flows south through the unit providing consistent water in lower reaches. Cottonwood Creek drainage and its north fork cut through mid-unit terrain.

Multiple smaller streams—Cedar Bar, Greyson, Clear, and Congdon—run intermittent to seasonal depending on snowmelt timing. Springs scatter across the higher benches but many run dry by late summer. Water availability is a key constraint on August-September hunting strategy.

Pronghorn are the primary species suited to Unit 390's open valley and sagebrush bench habitat. Early season hunts leverage spring-growth vegetation on lower elevations; mid-season finds animals shifting to thermal cover on higher benches. Late season pronghorn concentrate near remaining water sources and areas with active irrigation.

The rolling terrain allows effective glassing from ridgetops overlooking the open flats where pronghorn typically feed. Success requires identifying active migration routes between water and feeding areas. High terrain complexity means scouting thoroughly and mapping pronghorn patterns before season opens.

The mix of open country and scattered timber provides habitat but limited topographic funnels—expect to do considerable glassing and stalking rather than relying on narrow passes.