Illinois

The 21st state, almost too small to qualify

Illinois had to scramble to become a state. Congress’s Enabling Act of April 1818 required 40,000 residents, and when the territory’s census in June found only about 35,000, officials kept counting until December 1, finally reaching 40,258. Illinois was admitted on December 3, 1818, as the 21st state.

Its shape owes a lot to one man. The territory’s delegate in Congress, Nathaniel Pope, got the planned northern border moved about 60 miles north. That gave Illinois a shoreline on Lake Michigan, the site of Chicago, and the lead mines around Galena. Without that change, Chicago would be in Wisconsin.

The name

Illinois is named for the Illinois, or Illiniwek, a group of independent tribes, among them the Cahokia, Kaskaskia, Peoria and Tamaroa, who shared a language and a large territory in the central Mississippi valley. The French missionary Jacques Marquette wrote in the 1670s that the word meant “the men,” and that explanation was repeated for centuries. Newer studies of the language trace it instead to a word meaning roughly “he speaks in the ordinary way,” which the Ojibwa borrowed and passed on to French explorers.

Three capitals and the Long Nine

Illinois’s first capital was Kaskaskia, an old French town on the Mississippi at the southwestern edge of the state. In 1820 the government moved to Vandalia, nearer the middle, where it stayed for twenty years. In 1837 a group of Sangamon County legislators nicknamed the “Long Nine” for their combined height, among them a young Abraham Lincoln, persuaded the General Assembly to move the capital to Springfield, which became the capital in 1839. Lincoln practiced law there, served in the Old State Capitol, gave his “House Divided” speech there in 1858, and is buried there. The capital page tells the story.

Land of Lincoln, Prairie State

“Land of Lincoln” became the official state slogan in 1955 and has been on Illinois license plates ever since. The older nickname, “the Prairie State,” comes from the huge tallgrass prairies early settlers found, which once covered most of the state. Big bluestem, one of the tallest prairie grasses, is now the state grass. The motto on the state seal is “State Sovereignty, National Union.” After the Civil War, Secretary of State Sharon Tyndale wanted to put “National Union” first; when the Senate refused, he had the banner on the new seal twisted so that the word “Sovereignty” appears upside down.

Symbols from students

Illinois has 36 official symbols, and an unusual number came from students. Schoolchildren chose the cardinal in 1929, the violet and the oak in 1907-1908, the white-tailed deer in 1980, the monarch butterfly in 1975 and the bluegill in 1986. Later classes proposed popcorn as the state snack, the GoldRush apple, sweet corn and, in 2026, the black-and-gold bumblebee, which becomes the state bee in 2027. The state fossil is the Tully monster, a strange soft-bodied sea creature known almost only from Illinois. The most unusual symbol is the state microbe, a strain of Penicillium mold found on a cantaloupe in Peoria that made the mass production of penicillin possible during World War II. See every symbol on the Illinois symbols page.

The flag shows the eagle from the state seal on white, with the word ILLINOIS added in 1970 after a sailor in Vietnam found that nobody could identify it.

Land and people

Illinois covers 57,914 square miles, 25th among the states, and had about 12.7 million residents in 2025, sixth in the country, slightly fewer than in 2020. It borders Wisconsin, Iowa, Missouri, Kentucky and Indiana, and Lake Michigan to the northeast; the Mississippi River forms its entire western boundary. Chicago, with about 2.73 million people, is by far the largest city, home to more than a fifth of all Illinoisans. Aurora, Naperville, Joliet and Rockford follow, far behind.