Where is Winnebago County?

3 Winnebago Counties in 3 states · 468,143 people (2025)

There are 3 counties named Winnebago County in the United States, in Illinois, Iowa and Wisconsin. The most populous is Winnebago County, Illinois (county seat: Rockford), with 283,674 people in 2025. 3 of them are named after Ho-Chunk, Siouan-speaking Native American people.

Map of the United States showing where all 3 Winnebago Counties are, labeled by state
Every Winnebago County in the United States (red), labeled with its state. Boundaries: U.S. Census Bureau, 2025. Free to use with attribution (CC BY 4.0).

All 3 Winnebago Counties

Sorted by state. Each link opens the county's map.

StateCounty seatPopulation 2025Land area (sq mi)EstablishedNamed after
Winnebago County, IllinoisRockford283,6745131836Ho-Chunk
Winnebago County, IowaForest City10,2514011851Ho-Chunk
Winnebago County, WisconsinOshkosh174,2184351840Ho-Chunk

Questions about Winnebago Counties

How many Winnebago Counties are there?

There are 3 Winnebago Counties in the United States, in Illinois, Iowa and Wisconsin.

Which Winnebago County is the largest?

By population, Winnebago County, Illinois (283,674 people in 2025). By land area, Winnebago County, Illinois (513 sq mi).

Which Winnebago County is the oldest?

Winnebago County, Illinois, established in 1836. The newest is Winnebago County, Iowa (1851).

Why are there so many Winnebago Counties?

3 of the 3 are named after Ho-Chunk, Siouan-speaking Native American people. Many counties took their names from the same founders, presidents and generals as new states were organized.

How do I find out which Winnebago County an address is in?

Open the county map of the state: it has a search box for cities, towns and ZIP codes. On a phone, the "what county am I in" tool on our sister site uses your location.

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Other common county names