There were 3,157 households out of which 30.1% had children under the age of 18 living with them, 48.9% were married couples living together, 10.7% had a female householder with no husband present, and 36.6% were non-families. 32.5% of all households were made up of individuals and 15.0% had someone living alone who was 65 years of age or older. The average household size was 2.34 and the average family size was 2.97.
In the city the population was spread out with 25.3% under the age of 18, 8.5% from 18 to 24, 28.9% from 25 to 44, 21.5% from 45 to 64, and 15.8% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 91.1 males. For every 100 females age 18 and over, there were 89.1 males.
The median income for a household in the city was $36,279, and the median income for a family was $48,024. Males had a median income of $34,777 versus $22,296 for females. The per capita income for the city was $18,729. About 7.8% of families and 10.8% of the population were below the poverty line, including 15.9% of those under age 18 and 8.4% of those age 65 or over.
The major employers in Clinton, IL include the Clinton Nuclear Power Plant, John Warner Hospital, Walmart, and HNC Products Inc. The annual Apple and Pork Festival draws ten times or more of the population to the city to visit, partake, and purchase items typifying the town. Other attractions include the Dewitt County Fairgrounds, Weldon Springs, and Mr. Lincoln's Square, where Abraham Lincoln delivered a campaign address.