Yellowstone County, Montana

Yellowstone County
Yellowstone County Courthouse in Billings, 2024
Location within the U.S. state of Montana
Montana's location within the U.S.
Coordinates: 45°56′N 108°16′W / 45.94°N 108.27°W / 45.94; -108.27
Country United States
State Montana
FoundedFebruary 26, 1883
Named afterYellowstone River
SeatBillings
Largest cityBillings
Area
  Total
2,649 sq mi (6,860 km2)
  Land2,633 sq mi (6,820 km2)
  Water16 sq mi (40 km2)  0.6%
Population
 (2020)
  Total
164,731
  Estimate 
(2024)
171,583
  Density62/sq mi (24/km2)
Time zoneUTC−7 (Mountain)
  Summer (DST)UTC−6 (MDT)
Congressional district2nd
Websitewww.co.yellowstone.mt.gov
  • Montana county number 03

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 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 included in the Billings, Montana Metropolitan Statistical Area.