COUNTY · KY
Jefferson County, Kentucky
Jefferson County is a county in Kentucky with FIPS code 21111 and an estimated population of 772,144 (Census 2023), 1st largest of 120 in the state.
County facts
- Name
- Jefferson County
- State
- Kentucky
- Type
- county
- FIPS code
- 21111
- State FIPS
- 21
- Population (2023)
- 772,144
- Change since 2020
- -1.4%
- State rank
- 1 of 120
Population is the Census Bureau’s Vintage 2023 estimate.
Major cities in Jefferson County
Other counties in Kentucky
Questions
What is the FIPS code for Jefferson County?
Jefferson County, Kentucky has the five-digit FIPS code 21111: 21 for the state and 111 for the county.
What state is Jefferson County in?
Jefferson County is in Kentucky.
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.