Illinois (ˌɪlɪˈnɔɪ ) is a state in the Midwestern United States. The Great Lakes are to its northeast and the Mississippi River to its west. Its largest metropolitan areas are Chicago and the Metro East region of Greater St. Louis. Other metropolitan areas include Peoria and Rockford, as well as Springfield, its capital. Of the fifty U.S. states, Illinois has the fifth-largest gross domestic product (GDP), the sixth-largest population, and the 25th-largest land area.
Illinois has a highly diverse economy, with the global city of Chicago in the northeast, major industrial and agricultural hubs in the north and center, and natural resources such as coal, timber, and petroleum in the south. Owing to its central location and favorable geography, the state is a major transportation hub: the Port of Chicago has access to the Atlantic Ocean through the Great Lakes and Saint Lawrence Seaway and to the Gulf of Mexico from the Mississippi River via the Illinois Waterway. Additionally, the Mississippi, Ohio, and Wabash rivers form parts of the state's boundaries. Chicago's O'Hare International Airport has been among the world's ten busiest airports for decades. Illinois has long been considered a microcosm of the United States and a bellwether in American culture, exemplified by the phrase Will it play in Peoria?.
What is now Illinois was inhabited for thousands of years by various indigenous cultures, including the advanced civilization centered in the Cahokia region. The French were the first Europeans to arrive, settling near the Mississippi River in the 17th century in the region they called Illinois Country, as part of the sprawling colony of New France. Following U.S. independence in 1783, American settlers began arriving from Kentucky via the Ohio River, and the population grew from south to north. Illinois was part of the United States' oldest territory, the Northwest Territory, and in 1818 it achieved statehood.