COUNTY · IL
McDonough County, Illinois
McDonough County is a county in Illinois with FIPS code 17109 and an estimated population of 26,839 (Census 2023), 50th largest of 102 in the state.
County facts
- Name
- McDonough County
- State
- Illinois
- Type
- county
- FIPS code
- 17109
- State FIPS
- 17
- Population (2023)
- 26,839
- Change since 2020
- -1.0%
- State rank
- 50 of 102
Population is the Census Bureau’s Vintage 2023 estimate.
Questions
What is the FIPS code for McDonough County?
McDonough County, Illinois has the five-digit FIPS code 17109: 17 for the state and 109 for the county.
What state is McDonough County in?
McDonough County is in Illinois.
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.