COUNTY · MT
Yellowstone County, Montana
Yellowstone County is a county in Montana with FIPS code 30111 and an estimated population of 170,843 (Census 2023), 1st largest of 56 in the state.
County facts
- Name
- Yellowstone County
- State
- Montana
- Type
- county
- FIPS code
- 30111
- State FIPS
- 30
- Population (2023)
- 170,843
- Change since 2020
- +3.4%
- State rank
- 1 of 56
Population is the Census Bureau’s Vintage 2023 estimate.
Major cities in Yellowstone County
Other counties in Montana
Questions
What is the FIPS code for Yellowstone County?
Yellowstone County, Montana has the five-digit FIPS code 30111: 30 for the state and 111 for the county.
What state is Yellowstone County in?
Yellowstone County is in Montana.
How do I know if an address is in this county?
Use the address lookup. ZIP codes and city names can cross county lines, so an address is the reliable check.
Sources: U.S. Census Bureau geographic reference files; Census Bureau Population Estimates, Vintage 2023. Last reviewed 2026-10-27.