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. It is also one of the towns along the Ronald Reagan Trail, a series of roads that connect towns in central Illinois that were of importance to Reagan's early life. President Reagan attended and graduated from Eureka College. History Eureka was originally laid out as Walnut Grove in 1855. The name was changed to Eureka because of a naming conflict with another Walnut Grove. Sources differ on who proposed the name Eureka. The city is named from the Greek expression Eureka, meaning "I have found it". Geography Eureka is located at (40.715620, -89.275220). According to the 2010 census, Eureka has a total area of , of which (or 98.44%) is land and (or 1.56%) is water. Demographics As of the 2000 United States Census, there were 4,871 people, 1,754 households, and 1,169 families residing in the city. The population density was . There were 1,831 housing units at an average density of . The racial makeup of the city was 97.97% White, 0.57% African American, 0.37% Native American, 0.33% Asian, 0.16% from other races, and 0.60% from two or more races. Hispanic or Latino of any race were 1.03% of the population. There were 1,754 households, out of which 31.7% had children under the age of 18 living with them, 55.9% were married couples living together, 8.3% had a female householder with no husband present, and 33.3% were non-families. 30.7% of all households were made up of individuals, and 17.3% had someone living alone who was 65 years of age or older. The average household size was 2.46 and the average family size was 3.12. In the city, the population was spread out, with 24.3% under the age of 18, 14.5% from 18 to 24, 23.1% from 25 to 44, 16.9% from 45 to 64, and 21.1% who were 65 years of age or older. The median age was 36 years. For every 100 females, there were 85.2 males. The median income for a household in the city was $44,744, and the median income for a family was $53,590. Males had a median income