Yellowstone County is the most populous county in the U.S. state of Montana. As of the 2020 census, the population was 164,731. Its county seat is Billings, the state's most populous city. Like the nearby park, Yellowstone County is named after the Yellowstone River which roughly bisects the county, flowing southwest to northeast. The river, in turn, was named for the yellow sandstone cliffs in what is now Yellowstone County. Yellowstone County is included in the Billings, Montana Metropolitan Statistical Area.

Geography

According to the United States Census Bureau, the county has a total area of 2649 sqmi, of which 2633 sqmi is land and 16 sqmi (0.6%) is water.

Major highways

Transit

Adjacent counties

National protected areas

Demographics

2020 census

As of the 2020 census there were 164,731 people living in the county.

2010 census

As of the 2010 census, there were 147,972 people, 60,672 households, and 38,367 families residing in the county. The population density was 56.2 PD/sqmi. There were 63,943 housing units at an average density of 24.3 /sqmi. The racial makeup of the county was 90.7% white, 4.0% American Indian, 0.6% black or African American, 0.6% Asian, 0.1% Pacific islander, 1.2% from other races, and 2.8% from two or more races. Those of Hispanic or Latino origin made up 4.7% of the population. In terms of ancestry, 32.4% were German, 14.0% were Irish, 11.3% were English, 10.0% were American, and 9.9% were Norwegian. Of the 60,672 households, 30.5% had children under the age of 18 living with them, 48.0% were married couples living together, 10.5% had a female householder with no husband present, 36.8% were non-families, and 29.7% of all households were made up of individuals. The average household size was 2.38 and the average family size was 2.94. The median age was 38.3 years. The median income for a household in the county was $48,641 and the median income for a family was $62,380. Males had a median income of $42,899 versus $30,403 for females. The per capita income for the county was $26,152. About 7.9% of families and 11.2% of the population were below the poverty line, including 15.6% of those under age 18 and 7.7% of those age 65 or over.

Politics

Yellowstone County is very conservative for an urban county. Its voters have been reliably Republican for the better part of a century. Lyndon B. Johnson's 1964 landslide was the last time that the county voted for a Democratic candidate.

Communities

Cities

Town

Census-designated places

Other unincorporated communities

Ghost towns

Education

School districts include: K-12 (unified): High school districts: Elementary school districts: