Chicago, Illinois, located in the center of the Midwestern prairie on the banks of Lake Michigan, has always played a special role in the national imagination. Known as "The City of Neighborhoods," "The City of Broad Shoulders" (from a poem by Carl Sandburg) and "The City that Works," Chicago has been associated with an array of images, ranging from its reputation for political corruption to its fiercely "tribal" ethnic rivalries to its history of gangsters (particularly during the Prohibition era), to the violence that erupted during the Democratic National Convention of 1968, when the police and National Guard were unleashed by then-Mayor Richard J. Daley to quell antiwar demonstrations.

Chicago's cityscape bears the marks of its once unrivaled prominence as a center of industry though, like many of its companion rustbelt cities, manufacturing now employs only about one-fifth of workers (mostly in food processing). Chicago's once famous steelyards closed down in the early 1980s due to competition from cheaper steel produced abroad. Its location at the hub of the transcontinental train lines and its proximity to the cattleraising farms of the Midwest had made it the center of the meatpacking industry at the turn of the nineteenth century when the development of refrigerated train cars allowed freshly slaughtered meat to be safely shipped to markets in the East and elsewhere. The rise of trucking and the growth of the interstate highway system eventually obviated the need for a centralized location for meatpacking. Almost all the Chicago stockyards, whose appalling conditions had been immortalized by Upton Sinclair in his 1906 novel The Jungle, closed down between the 1930s and the 1960s.

Unlike many of the other rustbelt cities, however, Chicago has had the ability to reinvent itself, and, in the 1990s, it enjoyed an economic renaissance that seems to parallel its rebirth more than a century earlier after the famous fire of 1871. It remains the financial center of the Midwest and its main airport, O'Hare, is one of the busiest in the world. Old industrial areas which ring the central city (known as "the Loop" because of the pattern of elevated train tracks that surround the core) are now being redeveloped into loft apartments and condominiums, restaurants and artists' galleries; its natural setting on the banks of Lake Michigan is also being newly exploited. Lake Shore Drive, which runs along the lakefront from the city's northern tip to its southern tip, has been rerouted as it runs past the Loop so that institutions located on the Lake, including the Museum of Natural History the Aquarium and the Planetarium, are now easily accessible on foot, as is the lakefront itself. Chicago sports teams include the Bears (football), the Bulls (basketball), whose most famous former player is Michael Jordan and two baseball teams, the Cubs and the White Sox. Wrigley Stadium, home of the Cubs, is one of the few baseball parks still located in the middle of a city neighborhood, now known as "Wrigleyville." Chicago is also famous for its "Magnificent Mile" shopping district, on North Michigan Avenue, and the Art Institute.

Chicago hosts many immigrant communities, including East and West Europeans, Mexicans and Asians. Citizens of Japanese descent ended up in Chicago after being released from Midwestern internment camps following the Second World War. Its African American population increased rapidly in the Great Migration from the South between the World Wars and following the Second World War, so that they now make up about two-fifths of the city's residents. Overall, Chicago was demoted from second to third city in the US following the 1990 census, which the population of Los Angeles, CA surpassed.

In the 1980s, Chicago was roiled with political turmoil as its old Democratic Party "machine," which controlled the ward organizations and doled out patronage jobs and which had long been dominated by the city's "white ethnics," the Irish in particular, was overthrown with the election of the city's first African American mayor, Harold Washington. Despite the turmoil and racist invective that attended his first election in 1983, Washington proved a charismatic leader and was re-elected to office in 1987, although he died of a heart attack shortly thereafter. After an interim mayor, Richard M. Daley son of the famous Richard J. Daley was elected to office.

For social scientists, Chicago has always been associated with the Chicago School of Sociology, which flourished particularly during the 1920s and 1930s. These social scientists, based at the renowned University of Chicago, used the city as their laboratory They conducted empirical research on particular neighborhoods and occupational groups, with a special interest in social problems caused by poverty In the 1920s, a sociologist, Ernest W. Burgess, developed his theory that American cities were made up of "concentric zones," with an "administrative—business sector" at the center of the city surrounded by a ring of slums and ethnic enclaves, which, in turn, was surrounded by a zone of slightly better-off immigrant neighborhoods, which was encircled by Zone 4, where the American-born middle classes resided. Zone 5 housed the suburban commuters. This model fostered the development of a human ecology perspective on the city in which the urban environment was envisioned like a natural habitat made up of interconnected systems. Despite the fact that critics pointed out rather early on that the particular formation of Chicago and other cities was hardly "natural," but was the outcome of particular policies shaped by governmental and market interests, the "zonal development" model continued to be influential in urban studies.