Chicago, for much of its history, has been known informally as America's "Second City." It is currently ranked as the third-most populous city in the United States after New York and Los Angeles, with a population of nearly 3 million people. The Chicago metropolitan area (commonly referred to as Chicagoland) has a population of over 9.7 million people in Illinois, Wisconsin and Indiana, making it also the third largest metropolitan area in the U.S. Adjacent to Lake Michigan, it is among the world's twenty-five largest urban areas by population, and rated an alpha world city by the World Cities Study Group at Loughborough University.
Incorporated as a city in 1837 after being founded in 1833 at the site of a portage between the Great Lakes and the Mississippi River watershed, it soon became a major transportation hub in North America and quickly became the transportation, financial and industrial center of the American Midwest. Today the city's attractions bring 44.2 million visitors annually.
One of its most famous historical occurrences, the Great Chicago Fire was a conflagration that burned from Sunday October 8 to early Tuesday October 10, 1871, killing hundreds and destroying about four square miles in Chicago, Illinois. Though the fire was one of the largest U.S. disasters of the 19th century, the rebuilding that began almost immediately spurred Chicago's development into one of the most populous and economically important American cities. Perhaps the most outstanding of this development was the relocation of many of the nation's most prominent architects to the city from New England for construction of the 1893 World Columbian Exposition. Many architects including Burnham, Root, Adler and Sullivan went on to design other well known Chicago landmarks because of the Exposition.
In 1885, the first steel-framed high-rise building rose in Chicago ushering in the skyscraper era. Today, Chicago's skyline is among the world's tallest. Downtown's historic buildings include the Chicago Board of Trade Building in the Loop, with others along the lakefront and the Chicago River. Once first on the list of largest buildings in the world and still listed thirteenth, the Merchandise Mart stands near the junction of the north and south river branches. Presently the three tallest in the city are the Sears Tower, the Aon Center (previously the Standard Oil Building), and the John Hancock Center. This is soon to change with the addition of the Chicago Spire to Chicago’s skyline. The city's architecture includes lakefront high-rise residential towers, low-rise structures, and single-family homes.
Multiple kinds and scales of houses, townhouses, condominiums and apartment buildings can be found in Chicago. Large swaths of Chicago's residential areas away from the lake are characterized by bungalows built either during the early 20th century or after World War II.
