Musselshell County is a county in south-central Montana. As of the 2020 census, the population was 4,730. Its county seat is Roundup.

History
Musselshell County was created in 1911 by Montana Governor Edwin L. Norris. The area was taken from Fergus, from Yellowstone, and Meagher counties. It was named for the Musselshell River which runs southwest–northeast through the county. That river had been thus named in 1805 by the Lewis and Clark Expedition, due to the abundance of freshwater mussels found along its banks. In 1915, a western portion of the county was partitioned off to form Golden Valley County, giving Musselshell County its present boundaries.

The county's northwestern area is rolling grasslands, which slope southeastward to the Musselshell River and the forested Bull Mountains in the southeast. The county has abundant natural resources of coal deposits, subterranean oil, and timbered slopes.

Geography
According to the United States Census Bureau, the county has a total area of , of which  is land and  (0.1%) is water.

Major highways
  U.S. Highway 12
  U.S. Highway 87

Adjacent counties

 Fergus County - northwest
 Petroleum County - north
 Rosebud County - east
 Yellowstone County - south
 Golden Valley County - west

National protected area
 Lake Mason National Wildlife Refuge

Politics
In the fourteen national elections after its organization, Musselshell County voters selected Republican presidential candidates 50% of the time, and Democratic candidates 50% of the time. However, since the 1968 election, the Republican candidate has been selected in every election.

Demographics

2020 census
As of the census of 2020, there were 4,730 people.

2010 census
As of the census of 2010, there were 4,538 people, 2,046 households, and 1,276 families in the county. The population density was . There were 2,654 housing units at an average density of . The racial makeup of the county was 96.1% white, 1.3% American Indian, 0.2% black or African American, 0.2% Asian, 0.2% from other races, and 1.9% from two or more races. Those of Hispanic or Latino origin made up 2.6% of the population. In terms of ancestry, 28.1% were German, 16.5% were English, 16.1% were Irish, 7.6% were Norwegian, and 7.0% were American.

Of the 2,046 households, 23.2% had children under the age of 18 living with them, 52.4% were married couples living together, 6.5% had a female householder with no husband present, 37.6% were non-families, and 33.5% of all households were made up of individuals. The average household size was 2.19 and the average family size was 2.78. The median age was 49.1 years.

The median income for a household in the county was $37,033 and the median income for a family was $47,860. Males had a median income of $33,182 versus $25,750 for females. The per capita income for the county was $20,875. About 14.1% of families and 17.8% of the population were below the poverty line, including 28.6% of those under age 18 and 9.6% of those age 65 or over.

Communities

City
 Roundup (county seat)

Town
 Melstone

Unincorporated communities
 Delphia
 Elso
 Klein
 Queens Point

Census-designated places
 Camp Three
 Flat Willow Colony
 Kilby Butte Colony
 Klein
 Musselshell

See also
 List of lakes in Musselshell County, Montana
 List of mountains in Musselshell County, Montana
 National Register of Historic Places listings in Musselshell County, Montana

References

External links
 Musselshell County website

 
1911 establishments in Montana
Populated places established in 1911