Illinois (IPAc-enen-us-Illinois.ogg??l??n?? respellscil-i-scnoy), the 21st (List of U.S. states by date of statehood) state (U.S. state) admitted to the United States of America (United States), is the most populous and demographically diverse Midwestern (Midwestern United States) state and the fifth most populous state in the nation. With Chicago in the northeast, small industrial cities and great agricultural productivity in central and western Illinois, and natural resources like coal, timber, and petroleum in the south, Illinois has a broad economic base. Illinois is an important transportation hub; the Port of Chicago connects the Great Lakes to the Mississippi River via the Illinois River. Illinois is often viewed as a microcosm (Macrocosm and microcosm) of the United States; an Associated Press analysis of 21 demographic factors found Illinois the "most average state", while Peoria (Peoria, Illinois) has long been a proverbial social and cultural (Will it play in Peoria?) bellwether.

With a population near 40,000 between 1300 and 1400 AD, the Mississippian-culture (Mississippian culture) city of Cahokia, in what is now southern Illinois, was the largest city within the United States at the time, and kept its record until after 1790, when it was surpassed by New York City. Gradually Cahokia and the area were abandoned, and at the time of the American Revolution, only about 2,000 Native American hunters and a small number of French (Habitants) villagers inhabited the Illinois area. United States migrant settlers began arriving from Kentucky in the 1810s; Illinois achieved statehood (List of U.S. states by date of statehood) in 1818. The future metropolis of Chicago was founded in the 1830s on the banks of the Chicago River, one of the few natural harbors on southern Lake Michigan. Railroads (Rail transport) and John Deeres invention of the self-scouring steel plow (plough) made central Illinois rich prairie into some of the worlds most productive and valuable farmlands, attracting immigrant (immigration) farmers from Germany (German American) and Sweden (Swedish American).

By 1900, the growth of industrial jobs in the northern cities and coal mining in the central and southern areas attracted immigrants from Eastern (Eastern Europe) and Southern Europe. Its manufacturing made the state a major arsenal in both world wars. The Great Migration (Great Migration (African American)) of African Americans from the rural South to Chicago formed a large and important community (History of African Americans in Chicago) that created the citys famous jazz and blues cultures. Today, approximately 74% of the population of Illinois resides in the northeastern corner of the state, primarily within the city of Chicago and the surrounding area (Chicago Metropolitan Area).

Three U.S. Presidents (President of the United States) have been elected while they were living in IllinoismdashAbraham Lincoln, Ulysses S. Grant, and Barack Obama. However, the only US President actually born in Illinois was Ronald Reagan, who was born in Tampico (Tampico, Illinois), raised in Dixon (Dixon, Illinois), and attended college at Eureka (Eureka College). Lincoln is the only president buried in Illinois; he is interred at Oak Ridge Cemetery in Springfield. Today, Illinois demonstrates the importance of Lincolns legacy to the state by the official state slogan, Land of Lincoln, which is displayed on all state-issued license plates (Vehicle registration plates of Illinois).