History of Illinois

The history of the region and people of Illinois, from Indigenous societies and European colonization through its development as a U.S. state.

Mississippian culture: A network of Indigenous societies that flourished across much of eastern North America from about 800 to 1600 CE. Cahokia, near present-day St. Louis, was a major Mississippian center in the Illinois region.
Illinois Territory: A United States territory that existed from 1809 until Illinois became a state in 1818. Territorial status established the institutions that preceded statehood.
Abraham Lincoln: The sixteenth U.S. president, who lived and practiced law in Illinois before his election in 1860. His political career made Illinois central to the national crisis over slavery and Union.
Chicago: The largest city in Illinois, founded in the nineteenth century at the southwestern shore of Lake Michigan. Its rise as a transport and industrial hub became a defining strand of state history.
Illinois and the Underground Railroad: The network of people and routes that helped enslaved people escape through Illinois toward freedom before the Civil War. Illinois’s free-state status coexisted with restrictive laws and active antislavery resistance.
Cahokia: A large pre-Columbian Indigenous city near present-day Collinsville, Illinois, centered on monumental earthen mounds. Its scale and influence make it a defining early chapter in the region’s history.
Northwest Ordinance: A 1787 law that organized U.S. territory northwest of the Ohio River and set a path toward statehood. It provided the legal framework for Illinois’s territorial organization and admission.
Stephen A. Douglas: A U.S. senator from Illinois who championed popular sovereignty and debated Abraham Lincoln in 1858. His rivalry with Lincoln placed Illinois politics at the center of the slavery debate.
Haymarket affair: The 1886 labor protest and bombing in Chicago followed by a controversial trial and executions. The affair made Chicago a focal point in the national struggle over labor rights.
Mound Builders of Illinois: The Indigenous communities that built earthen mounds at sites across present-day Illinois over many centuries. Their sites preserve evidence of societies that predated European settlement.

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History of MissouriCompared with: Illinois entered the Union as a free state while neighboring Missouri entered as a slave state.