COUNTY · IN
Allen County, Indiana
Allen County is a county in Indiana with FIPS code 18003 and an estimated population of 394,545 (Census 2023), 3rd largest of 92 in the state.
County facts
- Name
- Allen County
- State
- Indiana
- Type
- county
- FIPS code
- 18003
- State FIPS
- 18
- Population (2023)
- 394,545
- Change since 2020
- +2.2%
- State rank
- 3 of 92
Population is the Census Bureau’s Vintage 2023 estimate.
Major cities in Allen County
Other counties in Indiana
Questions
What is the FIPS code for Allen County?
Allen County, Indiana has the five-digit FIPS code 18003: 18 for the state and 003 for the county.
What state is Allen County in?
Allen County is in Indiana.
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.