COUNTY · MO
Jefferson County, Missouri
Jefferson County is a county in Missouri with FIPS code 29099 and an estimated population of 231,230 (Census 2023), 7th largest of 115 in the state.
County facts
- Name
- Jefferson County
- State
- Missouri
- Type
- county
- FIPS code
- 29099
- State FIPS
- 29
- Population (2023)
- 231,230
- Change since 2020
- +1.9%
- State rank
- 7 of 115
Population is the Census Bureau’s Vintage 2023 estimate.
Questions
What is the FIPS code for Jefferson County?
Jefferson County, Missouri has the five-digit FIPS code 29099: 29 for the state and 099 for the county.
What state is Jefferson County in?
Jefferson County is in Missouri.
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.