what county is eureka, il in
Eureka is a city in Olio Township, Woodford County, Illinois, United States. The population was 5,295 at the 2010 census. It is the county seat of Woodford County. Eureka is part of the Peoria, Illinois Metropolitan Statistical Area. Eureka is a small community centered on the intersection of what is now U.S. 24 and Illinois 117.