Chicago is the largest city in the U.S. state of Illinois, as well as the third-most populous city in the United States with 2.8 million people. Known as the "Second City," the "Windy City," the "City of Big Shoulders," and "Chi-town" (along with other nicknames and colloquial nicknames that reflect the city's character), Chicago is located along the southwestern shore of Lake Michigan. When combined with its suburbs and nine surrounding counties in Illinois, Wisconsin, and Indiana, the greater metropolitan area known as Chicagoland encompasses a population of 9.3 million, making it the third-largest in the United States.

Growing from its 1833 founding as a frontier town of the Old Northwest into one of the world's premier cities, Chicago is ranked as one of 10 "Alpha" (most influential) world cities. Chicago today is the financial, economic, and cultural capital of the Midwest. The city is recognized as a major transportation, business, and architectural center of the United States. The city's skyscrapers, local cuisine, political traditions, and sports teams are some of its most recognized symbols.