Rock Island County | |
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![]() Rock Island County Justice Center | |
![]() Location within the U.S. state of Illinois | |
![]() Illinois's location within the U.S. | |
Coordinates: 41°28′N 90°34′W / 41.47°N 90.57°W | |
Country | ![]() |
State | ![]() |
Founded | 1831 |
Named for | Rock (Arsenal) Island |
Seat | Rock Island |
Largest city | Moline |
Area | |
• Total | 451 sq mi (1,170 km2) |
• Land | 428 sq mi (1,110 km2) |
• Water | 24 sq mi (60 km2) 5.2% |
Population (2020) | |
• Total | 144,672 |
• Estimate (2023) | 141,236 ![]() |
• Density | 320/sq mi (120/km2) |
Time zone | UTC−6 (Central) |
• Summer (DST) | UTC−5 (CDT) |
Congressional district | 17th |
Website | rockislandcountyil |
Rock Island County is a county located in the U.S. state of Illinois, bounded on the west by the Mississippi River. According to the 2020 census, it had a population of 144,672.[1] Its county seat is Rock Island; its largest city is neighboring Moline.[2] Rock Island County is one of the four counties that make up the Davenport-Moline-Rock Island, IA-IL Metropolitan Statistical Area.[3]