St. Clair County is a county located in the state of Illinois, and determined by the U.S. Census Bureau to include the mean center of U.S. population in 1970. As of 2000, the population is 256,082. Its county seat is Belleville, Illinois.

It is a part of the St. Louis metropolitan area. St. Clair County is also the first county established in the state of Illinois. It's existence actually precedes the state of Illinois as it was one of two counties established in the Northwestern Territories in 1790.

Geography

According to the U.S. Census Bureau, the county has a total area of 1,746 km² (674 mi²). 1,719 km² (664 mi²) of it is land and 26 km² (10 mi²) of it is water. The total area is 1.51% water.

Demographics

As of the census² of 2000, there are 256,082 people, 96,810 households, and 67,282 families residing in the county. The population density is 149/km² (386/mi²). There are 104,446 housing units at an average density of 61/km² (157/mi²). The racial makeup of the county is 67.94% White, 28.77% Black or African American, 0.26% Native American, 0.91% Asian American, 0.05% Pacific Islander, 0.80% from other races, and 1.29% from two or more races. 2.19% of the population are Hispanic or Latino of any race.

There are 96,810 households out of which 34.50% have children under the age of 18 living with them, 48.10% are married couples living together, 17.10% have a female householder with no husband present, and 30.50% are non-families. 25.90% of all households are made up of individuals and 10.30% have someone living alone who is 65 years of age or older. The average household size is 2.59 and the average family size is 3.13.

In the county the population is spread out with 27.70% under the age of 18, 8.90% from 18 to 24, 29.20% from 25 to 44, 21.10% from 45 to 64, and 13.20% who are 65 years of age or older. The median age is 35 years. For every 100 females there are 91.40 males. For every 100 females age 18 and over, there are 87.20 males.

The median income for a household in the county is $39,148, and the median income for a family is $47,409. Males have a median income of $36,569 versus $25,773 for females. The per capita income for the county is $18,932. 14.50% of the population and 11.80% of families are below the poverty line. Out of the total population, 21.60% of those under the age of 18 and 9.80% of those 65 and older are living below the poverty line.

Cities and towns

• Alorton
• Belleville
• Brooklyn
• Cahokia
• Caseyville
• Centreville
• Dupo
• East Carondelet
• East St. Louis
• Fairview Heights
• Fayetteville
• Freeburg
• Lebanon
• Lenzburg
• Marissa
• Mascoutah
• Millstadt
• New Athens
• O'Fallon
• Sauget
• Scott AFB
• Shiloh
• Smithton
• St. Libory
• Summerfield
• Swansea
• Washington Park