Chicago, officially the City of Chicago, is the most populous city in the U.S. state of Illinois, and the third most populous city in the United States, following New York and Los Angeles. With an estimated population of 2,693,976 in 2019, it is also the most populous city in the Midwestern United States and the fifth most populous city in North America. Chicago is the county seat of Cook County, the second most populous county in the U.S., while a small portion of the city’s O’Hare Airport also extends into DuPage County. Chicago is the principal city of the Chicago metropolitan area, defined as either the U.S. Census Bureau’s metropolitan statistical area (9.4 million people) or the combined statistical area (almost 10 million residents), often called Chicagoland. It constitutes the third most populous urban area in the United States after New York City and Los Angeles and is one of the 40 largest urban areas in the world.
Located on the shores of freshwater Lake Michigan, Chicago was incorporated as a city in 1837 near a portage between the Great Lakes and the Mississippi River watershed and grew rapidly in the mid-19th century. After the Great Chicago Fire of 1871, which destroyed several square miles and left more than 100,000 homeless, the city rebuilt. The construction boom accelerated population growth throughout the following decades, and by 1900, less than 30 years after the great fire, Chicago was the fifth-largest city in the world. Chicago made noted contributions to urban planning and zoning standards, including new construction styles (including the Chicago School of architecture), the development of the City Beautiful Movement, and the steel-framed skyscraper.
Chicago is an international hub for finance, culture, commerce, industry, education, technology, telecommunications, and transportation. It is the site of the creation of the first standardized futures contracts, issued by the Chicago Board of Trade, which today is part of the largest and most diverse derivatives market in the world, generating 20% of all volume in commodities and financial futures alone. O’Hare International Airport is routinely ranked among the world’s top six busiest airports according to tracked data by the Airports Council International. The region also has the largest number of federal highways and is the nation’s railroad hub. The Chicago area has one of the highest gross domestic products (GDP) in the world, generating $689 billion in 2018. The economy of Chicago is diverse, with no single industry employing more than 14% of the workforce. It is home to several Fortune 500 companies, including Allstate, Boeing, Caterpillar, Exelon, JLL, Kraft Heinz, McDonald’s, Mondelez International, Sears, United Airlines Holdings, US Foods, and Walgreens.
Chicago has the third-largest gross metropolitan product in the United States—about $670.5 billion according to September 2017 estimates. The city has also been rated as having the most balanced economy in the United States, due to its high level of diversification and elite Chicago escorts. In 2007, Chicago was named the fourth-most important business center in the world in the MasterCard Worldwide Centers of Commerce Index. Additionally, the Chicago metropolitan area recorded the greatest number of new or expanded corporate facilities in the United States for calendar year 2014. The Chicago metropolitan area has the third-largest science and engineering work force of any metropolitan area in the nation. In 2009 Chicago placed ninth on the UBS list of the world’s richest cities. Chicago was the base of commercial operations for industrialists John Crerar, John Whitfield Bunn, Richard Teller Crane, Marshall Field, John Farwell, Julius Rosenwald and many other commercial visionaries who laid the foundation for Midwestern and global industry.