Illinois
Prairie State · Capital: Springfield · Midwest (Midwest Rust)
Show simplified tile view
Quick stats
Bordering states: Wisconsin, Iowa, Missouri, Kentucky, Indiana.
About Illinois
Illinois is a Midwestern state reaching about 385 miles from the Wisconsin line to Cairo, where the Ohio meets the Mississippi. The Mississippi forms its entire western edge, the Ohio its southern one and the Wabash much of the Indiana line, and about 63 miles of Lake Michigan shore lie in the northeast. Ice sheets flattened most of the state into a till plain, leaving only 956 feet between Charles Mound and Cairo; the northwest corner and the Shawnee Hills of the far south escaped the ice. Tallgrass prairie once covered about 60 percent of the land and left deep, fertile soil.
Around 1100 Cahokia, opposite present day St. Louis, held perhaps 10,000 to 20,000 people. Marquette and Jolliet came down the Mississippi in 1673, French villages followed, and George Rogers Clark took Kaskaskia for Virginia in 1778. Illinois became the 21st state on 3 December 1818, after delegate Nathaniel Pope had its northern line set at 42 degrees 30 minutes, adding the site of Chicago. The capital moved to Springfield in 1839, and Lincoln and Douglas debated across the state in 1858. Linked to the Mississippi by canal in 1848, Chicago burned in 1871 and rebuilt with the Home Insurance Building of 1885, the first steel framed skyscraper.
The 2020 census counted 12,812,508 residents, 0.1 percent fewer than in 2010, and the state lost a House seat, keeping 17. From 1916 the Great Migration brought hundreds of thousands of Black southerners north, musicians such as Muddy Waters and Mahalia Jackson among them, and in 1942 Enrico Fermi's team achieved the first self-sustaining nuclear chain reaction at the University of Chicago. Illinois grows more pumpkins than any other state and ranks at the top in corn and soybeans. Ronald Reagan, born in Tampico in 1911, is the only president born in the state, and Walt Disney and Miles Davis were also Illinois natives.
4 fun facts about Illinois
- Chicago invented the skyscraper, the Home Insurance Building (1885) was the first.
- Lincoln spent most of his political career in Springfield, IL, but was born in Kentucky.
- Illinois grows more pumpkins than any other state, including most of the canned pumpkin sold in the US.
- Route 66 starts in Chicago and ends in Santa Monica, CA.
More about Illinois
Illinois geography and climate
Frequently asked questions about Illinois
Is Illinois a US state?
Yes, Illinois is one of the 50 US states. It was admitted to the Union in 1818, making it the 21st state. Its capital is Springfield and its largest city is Chicago.
What is the capital of Illinois?
The capital of Illinois is Springfield. Note that the largest city in Illinois is Chicago, not the capital, a common point of confusion.
When did Illinois become a state?
Illinois became a US state in 1818. It is the 21st state admitted to the Union.
What is the abbreviation for Illinois?
The 2-letter USPS abbreviation for Illinois is IL.
How big is Illinois?
Illinois ranks #25 of 50 US states by area. With 230.8 residents per square mile in 2020, it was the 12th most densely populated state.
What is the population of Illinois?
Illinois had 12,812,508 residents at the 2020 census, the 6th largest population of the 50 states, down 0.1% since 2010. That count gives it 17 seats in the US House of Representatives.
What region is Illinois in?
Illinois is in the Midwest region of the United States, per the US Census Bureau.
What time zone is Illinois in?
Illinois observes Central Time.
Learn more
How to learn the 50 states (full guide)
Last updated: