On Dec. 3, 1818, Illinois became the 21^st state to join the Union. This followed Illinois’ status as a territory since 1809, which represented a much larger border including Wisconsin and parts of Minnesota and Michigan.

The capital in 1818 was Kaskaskia, and in 1819 became Vandalia. At the time Illinois became a state the population was 34,620 residents. Most of the land in Illinois was largely unsettled. Many Native American tribes were pushed off their land and conflicted with colonists following Illinois’ statehood. The state’s first elected governor was Shadrach Bond, who ran without opposition. While Illinois joined as a free state, slavers were grandfathered in and were allowed to keep their slaves. Slavery was eliminated gradually, though anti-Black laws and other forms of segregation and institutionalized racism persisted.

Illinois is the fifth largest economy, sixth largest state by population and 25^th by land area. The state’s area is near that of England or Nepal. Illinois matches Turkey by economy, making it equivalent to the 16^th largest economy on Earth when measured by nominal GDP. The state topped national economic development rankings in 2024.