Winnebago County, Illinois

Winnebago County
County
Winnebago County Justice Center
Seal
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 / 42.33; -89.16
Country	United States
State	Illinois
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.wincoil.us

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.