Winnebago County | |
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Winnebago County Justice Center | |
![]() Location within the U.S. state of Illinois | |
![]() Illinois's location within the U.S. | |
Coordinates: 42°20′N 89°10′W / 42.33°N 89.16°W | |
Country | ![]() |
State | ![]() |
Founded | January 16, 1836 |
Named for | Winnebago people |
Seat | Rockford |
Largest city | Rockford |
Area | |
• Total | 519 sq mi (1,340 km2) |
• Land | 513 sq mi (1,330 km2) |
• Water | 5.9 sq mi (15 km2) 1.1% |
Population (2020) | |
• Total | 285,350 |
• Estimate (2023) | 280,922 ![]() |
• Density | 550/sq mi (210/km2) |
Time zone | UTC−6 (Central) |
• Summer (DST) | UTC−5 (CDT) |
Congressional districts | 16th, 17th |
Website | www |
Winnebago County is a county located in the U.S. state of Illinois. According to the 2020 census, it had a population of 285,350 making it the seventh most populous county in Illinois behind Cook County and its five surrounding collar counties. Its county seat is Rockford.[1] Winnebago County is the central county of the Rockford metropolitan area.