COUNTY · IL

Rock Island County, Illinois

Rock Island County is a county in Illinois with FIPS code 17161 and an estimated population of 141,236 (Census 2023), 14th largest of 102 in the state.

County facts

Name: Rock Island County
State: Illinois
Type: county
FIPS code: 17161
State FIPS: 17
Population (2023): 141,236
Change since 2020: -2.2%
State rank: 14 of 102

Population is the Census Bureau’s Vintage 2023 estimate.

Other counties in Illinois

Cook County DuPage County Lake County Will County Kane County McHenry County Winnebago County Madison County All 102

Questions

What is the FIPS code for Rock Island County?

Rock Island County, Illinois has the five-digit FIPS code 17161: 17 for the state and 161 for the county.

What state is Rock Island County in?

Rock Island 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.