Madison County was established on September 14, 1812. It was formed from parts of Randolph and St. Clair counties and named for President James Madison. At the time of its formation, Madison County included all of the modern State of Illinois north of St. Louis, as well as all of Wisconsin, part of Minnesota, and Michigan's Upper Peninsula. In the late 19th century, Madison County became an industrial region, and in the 20th century was known first for Graniteware, and later for its steel mills, oil refineries, and other heavy industries. The county had a large working population, and the county and surrounding area was a center of strength for the Democratic Party. Industrial restructuring cost many jobs and reduced the population. The county now is part of semi-rural, sparsely populated east of the St. Louis metropolitan area, as is neighboring St. Clair County. In 2009, the EPA issued an air pollution report that ranked Madison County as the county with the second-highest cancer risk in the country due to air pollution, second only to Los Angeles County, California.
Geography
According to the U.S. Census Bureau, the county has a total area of, of which is land and is water. Madison County is on the Mississippi River, while the other major body of water is Horseshoe Lake.
Climate and weather
In recent years, average temperatures in the county seat of Edwardsville have ranged from a low of in January to a high of in July, although a record low of was recorded in January 1977 and a record high of was recorded in July 2012. Average monthly precipitation ranged from in January to in May. Climate Zone 4A per the International Energy Conservation Code.
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. There were 117,106 housing units at an average density of. 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.
Like much of southern Illinois, Madison County was a predominantly Democratic area for much of its history, but in recent elections has been moving towards the Republicans. Mitt Romney narrowly carried the county in the 2012 presidential election, becoming the first Republican presidential nominee to do so since 1984. In 2016, Donald Trump carried the largest share of the vote for any Republican presidential candidate since 1972. The county also supported the Republican candidates for governor in 2010 and 2014.
