Officially known as Chicago, the City of Chicago is the largest city in the United States. The state of Illinois is the third most populous US city, after Los Angeles and New York City. It is the third-most populous Midwestern city and fifth in North America, with a population of 2,746,388 as of the 2020 census. Chicago is the County Seat in Cook County. It is also home to the second-most populous U.S. County. It is the most populated urban area in the entire world.

Chicago is a financial center of the world. It was the location of the first standard futures contracts. They were issued by Chicago Board of Trade. Today, it is one of the most important and largest financial institutions in the world. Diverse derivatives market, which generates 20% of all commodities volume and financial futures volume. According to Airports Council International's tracked data, O'Hare International Airport consistently ranks among the top six busiest airports in the world. It also boasts the most federal highways, and is the country's railway hub.. The Chicago area has one of the highest gross domestic products (GDP) in the world, generating $689 billion in 2018.[16] The economy of Chicago is diverse, with no single industry employing more than 14% of the workforce.