COUNTY · ID
Boundary County, Idaho
Boundary County is a county in Idaho with FIPS code 16021 and an estimated population of 13,557 (Census 2023), 25th largest of 44 in the state.
County facts
- Name
- Boundary County
- State
- Idaho
- Type
- county
- FIPS code
- 16021
- State FIPS
- 16
- Population (2023)
- 13,557
- Change since 2020
- +11.7%
- State rank
- 25 of 44
Population is the Census Bureau’s Vintage 2023 estimate.
Questions
What is the FIPS code for Boundary County?
Boundary County, Idaho has the five-digit FIPS code 16021: 16 for the state and 021 for the county.
What state is Boundary County in?
Boundary 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.