**Clinton County** is a county located in the U.S. State of Illinois, and determined by the U.S. Census Bureau to include the mean center of U.S. population in 1960. As of 2000, the population is 35,535. Its name is in honor of the seventh Governor of New York State, DeWitt Clinton. Its county seat is Carlyle, Illinois.

There are 12,754 households out of which 35.10% have children under the age of 18 living with them, 60.10% are married couples living together, 8.40% have a female householder with no husband present, and 27.70% are non-families. 24.20% of all households are made up of individuals and 11.90% have someone living alone who is 65 years of age or older. The average household size is 2.60 and the average family size is 3.10.

In the county the population is spread out with 24.90% under the age of 18, 9.30% from 18 to 24, 30.20% from 25 to 44, 21.30% from 45 to 64, and 14.40% who are 65 years of age or older. The median age is 37 years. For every 100 females there are 106.60 males. For every 100 females age 18 and over, there are 106.80 males.

The median income for a household in the county is $44,618, and the median income for a family is $52,580. Males have a median income of $36,035 versus $23,506 for females. The per capita income for the county is $19,109. 6.40% of the population and 4.60% of families are below the poverty line. Out of the total people living in poverty, 7.80% are under the age of 18 and 6.00% are 65 or older.