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 (nicknamed "Metro East"), 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.
Madison County between its creation in 1812 and 1815, extending north to Lake Superior and the border with Rupert's Land
Madison County between 1815 and 1817
Madison County between 1817 and 1821
Madison County between 1821 and 1825
Between 1825 and 1829, Madison included a northern salient that was split off to form part of Macoupin County.
In 1829 Madison returned to its 1821 borders.
In 1843 a small amount of land was transferred to Bond County, reducing Madison to its current size.