Beaverhead County, Montana

Beaverhead County is a county in Montana, United States, straddling the Continental Divide along the Idaho border in the state’s southwest corner. It had a population of 9,371 at the 2020 census and covers 5,572 square miles (14,430 km2) — the largest county in Montana by land area — centred near 45°07′N 112°54′W.

Dillon is the county seat, and its postal code is 59725. The county has one city, one incorporated town, and ten census-designated places, plus several historic mining and ranching communities that never incorporated. Montana has no civil townships, so places here are organised only as incorporated or unincorporated. Beaverhead County sits in the Mountain time zone; its FIPS code is 30-001.

Towns & Villages in Beaverhead County

The county’s population centres range from Dillon, home to University of Montana Western and more than four in five county residents, down to ranching hamlets of a few dozen people scattered across the Big Hole and Beaverhead valleys. CDP = census-designated place (unincorporated but tracked separately by the Census Bureau); Unincorp. = an unincorporated place with no census designation.

Bannack, Montana’s first territorial capital, is preserved as Bannack State Park rather than an active community; it is listed here for historical completeness, not as a populated place. Glendale and Elkhorn were both 19th-century silver-mining camps tied to the same Hecla Mining Company district; Elkhorn’s smelter town has been abandoned since the mine closed.

ZIP Codes

• 59725 — Dillon (county seat, serves the surrounding Beaverhead Valley)
• 59739 — Lima (also serves Monida and the Red Rock Lakes area)
• 59761 — Wisdom (serves the upper Big Hole Valley)
• 59762 — Wise River (serves the lower Big Hole Valley)
• 59732 — Glen
• 59736 — Jackson
• 59746 — Polaris (also serves Elkhorn Hot Springs and Maverick Mountain)
• 59724 — Dell (post office box service only)

Argenta, Dewey, Grant, Lakeview, Bannack, and Glendale have no dedicated ZIP code and are served by the nearest post office listed above.

Geography

Beaverhead County is dominated by the Beaverhead and Big Hole river valleys, broad ranching basins hemmed in by the Pioneer, Ruby, and Beaverhead mountain ranges. The Continental Divide runs along almost the entire western and southern county line, doubling as the Montana–Idaho state border. Clark Canyon Reservoir, formed by a dam on the Beaverhead River south of Dillon, is the county’s largest body of water and covers the site of the historic Camp Fortunate, where the Lewis and Clark Expedition met the Shoshone in 1805.

The county borders Ravalli County to the northwest, Deer Lodge County and Silver Bow County to the north, and Madison County to the east. Across the Continental Divide to the south and west lie three Idaho counties: Lemhi County, Clark County, and Fremont County.

Demographics

Beaverhead County had 9,371 residents at the 2020 census, giving it a density of about 1.7 people per square mile — among the most sparsely populated counties in the Lower 48. Dillon is by far the largest community, followed by Lima. The county’s median household income runs below the Montana median of $70,804, reflecting an economy still centred on ranching rather than higher-wage service or resource-extraction jobs found elsewhere in the state.

Economy & Local Life

Cattle ranching and hay production anchor the county’s economy, with the Big Hole Valley — nicknamed the “Land of 10,000 Haystacks” — still using some of the last beaverslide hay stackers in the country. Barretts Minerals operates one of the world’s largest talc mines near Dillon, and Barrett Hospital & HealthCare is one of the county’s largest employers. University of Montana Western, a four-year public university in Dillon, drives much of the town’s population and services base. Fly fishing on the Beaverhead and Big Hole Rivers draws visitors each summer.

History

Beaverhead County was created in 1865, one of Montana Territory’s original nine counties, and takes its name from Beaverhead Rock, a rock formation south of Dillon that the Shoshone likened to a swimming beaver’s head. Bannack, now a state park in the county’s southwest corner, was Montana’s first territorial capital, founded after an 1862 gold strike that touched off the Montana gold rush. Dillon itself grew up around the Utah and Northern Railway in 1880 and took the county seat from Bannack the same decade.

Getting There

Interstate 15 runs the length of the county north-south, connecting Dillon to Butte and Bozeman to the north and to Idaho Falls, Idaho, to the south. Montana Highway 278 and Montana Highway 43 serve the Big Hole Valley communities of Wisdom and Wise River.

• Butte — 65 miles north
• Bozeman — 130 miles northeast
• Idaho Falls, Idaho — 90 miles south
• Missoula — 150 miles northwest

Dillon Airport (DLN) offers general aviation; the nearest commercial airport is Bert Mooney Airport in Butte.

Frequently Asked Questions

Where is Beaverhead County, Montana?
It is in southwestern Montana along the Idaho border, roughly 65 miles south of Butte.

What is the population of Beaverhead County?
9,371 residents at the 2020 census.

How big is Beaverhead County?
5,572 square miles (14,430 km2), making it Montana’s largest county by land area.

What is the county seat of Beaverhead County?
Dillon is the county seat.

How many towns are in Beaverhead County?
One city (Dillon), one incorporated town (Lima), and ten census-designated places, plus several unincorporated and historic communities.

What ZIP codes are in Beaverhead County?
Eight ZIP codes serve the county, led by 59725 (Dillon) and 59739 (Lima).

What is Bannack, Montana?
Bannack was Montana’s first territorial capital and gold-rush boomtown; it is now preserved as Bannack State Park, an unpopulated ghost town.

More counties in this state: Towns and villages in Montana.