
Rock Island County
- State:
- Illinois
- County Seat:
- Rock Island
Rock Island County's estimated 2025 population is 140,590 with a growth rate of -0.23% in the past year according to the most recent United States census data. Rock Island County is the 15th largest county in Illinois. The 2010 population was 147,613 and has seen a growth of -4.76% since that time.