Winnebago County, Illinois

county in Illinois, United States

Winnebago County is a county in the U.S. state of Illinois. According to the 2010 census, it had a population of 295,266,[1] making it the seventh most populous county in Illinois after Cook County. Its county seat is Rockford.[2]

Winnebago County
City Hall in Rockford, Illinois.
City Hall in Rockford, Illinois.
Map of Illinois highlighting Winnebago County
Location within the U.S. state of Illinois
Map of the United States highlighting 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
FoundedJanuary 16, 1836
Named forWinnebago Tribe
Largest cityRockford
 • Total519 sq mi (1,340 km2)
 • Land513 sq mi (1,330 km2)
 • Water5.9 sq mi (15 km2)  1.1%%
 • Total295,266
 • Density575/sq mi (222/km2)
Time zoneUTC−6 (Central)
 • Summer (DST)UTC−5 (CDT)
Congressional districts16th, 17th

Winnebago County was founded on January 16, 1836 and named for the Winnebago Tribe of American Indians.


  1. "State & County QuickFacts". United States Census Bureau. Retrieved July 9, 2014.
  2. "Find a County". National Association of Counties. Retrieved 2011-06-07.