COUNTY · KS
Allen County, Kansas
Allen County is a county in Kansas with FIPS code 20001 and an estimated population of 12,412 (Census 2023), 36th largest of 105 in the state.
County facts
- Name
- Allen County
- State
- Kansas
- Type
- county
- FIPS code
- 20001
- State FIPS
- 20
- Population (2023)
- 12,412
- Change since 2020
- -1.0%
- State rank
- 36 of 105
Population is the Census Bureau’s Vintage 2023 estimate.
Questions
What is the FIPS code for Allen County?
Allen County, Kansas has the five-digit FIPS code 20001: 20 for the state and 001 for the county.
What state is Allen County in?
Allen County is in Kansas.
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.