Jefferson County, Illinois

Jefferson County is a county in Illinois with an estimated population of 36,320 in 2023. 8 cities, towns and Census places in it are indexed here.

Largest places in Jefferson County

About Jefferson County

Jefferson County is one of the counties of Illinois. County governments in Illinois handle local services such as courts, property records and elections; cities and towns inside the county run their own municipal services. Population figures come from the Census Bureau's Vintage 2023 estimates, which are updated annually.