COUNTY · ID
Ada County, Idaho
Ada County is a county in Idaho with FIPS code 16001 and an estimated population of 524,673 (Census 2023), 1st largest of 44 in the state.
County facts
- Name
- Ada County
- State
- Idaho
- Type
- county
- FIPS code
- 16001
- State FIPS
- 16
- Population (2023)
- 524,673
- Change since 2020
- +5.3%
- State rank
- 1 of 44
Population is the Census Bureau’s Vintage 2023 estimate.
Major cities in Ada County
Other counties in Idaho
Questions
What is the FIPS code for Ada County?
Ada County, Idaho has the five-digit FIPS code 16001: 16 for the state and 001 for the county.
What state is Ada County in?
Ada County is in Idaho.
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.