COUNTY · IL
Lake County, Illinois
Lake County is a county in Illinois with FIPS code 17097 and an estimated population of 708,760 (Census 2023), 3rd largest of 102 in the state.
County facts
- Name
- Lake County
- State
- Illinois
- Type
- county
- FIPS code
- 17097
- State FIPS
- 17
- Population (2023)
- 708,760
- Change since 2020
- -0.6%
- State rank
- 3 of 102
Population is the Census Bureau’s Vintage 2023 estimate.
Questions
What is the FIPS code for Lake County?
Lake County, Illinois has the five-digit FIPS code 17097: 17 for the state and 097 for the county.
What state is Lake County in?
Lake 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.