Madison County is a county in the U.S. state of Illinois. It is a part of the Metro East in southern Illinois. According to the 2010 census, it had a population of 269,282. The county seat is Edwardsville and largest city is Granite City,
According to the U.S. Census Bureau, the county has a total area of 741 square miles (1,920 km), of which 716 square miles (1,850 km) is land and 25 square miles (65 km) (3.4%) is water. Madison County is on the Mississippi River, while the other major body of water is Horseshoe Lake.
As of the 2010 census, there were 269,282 people, 108,094 households, and 71,756 families residing in the county. The population density was 376.3 inhabitants per square mile (145.3/km). There were 117,106 housing units at an average density of 163.7 per square mile (63.2/km). The racial makeup of the county was 88.2% white, 7.9% black or African American, 0.8% Asian, 0.2% American Indian, 0.9% from other races, and 1.8% from two or more races. Those of Hispanic or Latino origin made up 2.7% of the population. In terms of ancestry, 32.7% were German, 14.9% were Irish, 10.5% were English, 7.5% were American, and 5.7% were Italian.
Of the 108,094 households, 31.4% had children under the age of 18 living with them, 49.3% were married couples living together, 12.2% had a female householder with no husband present, 33.6% were non-families, and 26.8% of all households were made up of individuals. The average household size was 2.46 and the average family size was 2.98. The median age was 38.6 years.
The median income for a household in the county was $51,941 and the median income for a family was $64,630. Males had a median income of $50,355 versus $35,543 for females. The per capita income for the county was $26,127. About 9.1% of families and 12.9% of the population were below the poverty line, including 19.3% of those under age 18 and 6.6% of those age 65 or over.