Yellowstone County
Sign in to savecounty in Montana, United States
Key facts
- Country
- United States
- State
- Montana
- Founded
- February 26, 1883 (created), May 1, 1883 (organized)
- Named after
- Yellowstone River
- Seat
- Billings
- Largest city
- Billings
- Total
- 2,649.035 sq mi (6,860.97 km )
- Land
- 2,633.402 sq mi (6,820.48 km )
- Water
- 15.633 sq mi (40.49 km ) 0.59%
- Estimate 2025
- 172,692
- Density
- 62.5544/sq mi (24.1524/km )
- Time zone
- UTC−7 ( Mountain )
- Summer dst
- UTC−6 ( MDT )
- Congressional district
- 2nd
- Website
- yellowstonecountymt.gov
via Wikipedia infobox
Article
Yellowstone County is a county in the U.S. state of Montana. As of the 2020 census, the population was 164,731, and was estimated to be 172,692 in 2025, making it the most populous county in Montana. The county seat and the largest city is Billings, the most populous city in Montana and the 253rd-most populous city in the United States. It contains over 15.09% of the state's population. Like the nearby national 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 part of the Billings metropolitan area, which comprises all of Carbon, Stillwater, and Yellowstone Counties.