The buildings and architecture of Chicago have influenced and reflected the history of American architecture. The built environment of Chicago is reflective of the city's history and multicultural heritage, featuring prominent buildings in a variety of styles by many important architects. Since most structures within the downtown area were destroyed by the Great Chicago Fire in 1871 (the most famous exception being the Water Tower) Chicago buildings are noted for their originality rather than their antiquity.
Beginning in the early 1880s, architectural pioneers of the Chicago School explored steel-frame construction and, in the 1890s, the use of large areas of plate glass. These were among the first modern skyscrapers. William LeBaron Jenney's Home Insurance Building was completed in 1885 and is considered to be the first to use steel in its structural frame instead of cast iron. However, this building was still clad in heavy brick and stone. The Montauk Building, designed by John Wellborn Root Sr. and Daniel Burnham, was built from 1882 to 1883 using structural steel. Daniel Burnham and his partners, John Welborn Root and Charles Atwood, designed technically advanced steel frames with glass and terra cotta skins in the mid-1890s, in particular the Reliance Building; these were made possible by professional engineers, in particular E. C. Shankland, and modern contractors, in particular George A. Fuller.
Louis Sullivan was perhaps the city's most philosophical architect. Realizing that the skyscraper represented a new form of architecture, he discarded historical precedent and designed buildings that emphasized their vertical nature. This new form of architecture, by Jenney, Burnham, Sullivan, and others, became known as the "Commercial Style," but it was called the "Chicago School" by later historians.
In 1892, the Masonic Temple surpassed the New York World Building, breaking its two-year reign as the tallest skyscraper, only to be surpassed itself two years later by another New York building.
Numerous architects have constructed landmark buildings of varying styles in Chicago. Among them are the so-called "Chicago seven": James Ingo Freed, Tom Beeby, Larry Booth, Stuart Cohen, James Nagle, Stanley Tigerman, and Ben Weese.
Daniel Burnham led the design of the "White City" of the 1893 World's Columbian Exposition which some historians claim led to a revival of Neo-Classical architecture throughout Chicago and the entire United States. It is true that the "White City" represented anything other than its host city's architecture. While Burnham did develop the 1909 "Plan for Chicago", perhaps the first comprehensive city plan in the U.S, in a Neo-Classical style, many of Chicago's most progressive skyscrapers occurred after the Exposition closed, between 1894 and 1899. Louis Sullivan said that the fair set the course of American architecture back by two decades, but even his finest Chicago work, the Schlesinger and Meyer (later Carson, Pirie, Scott) store, was built in 1899—five years after the "White City" and ten years before Burnham's Plan.
Sullivan's comments should be viewed in the context of his complicated relationship with Burnham. Erik Larson's history of the Columbian Exposition, The Devil in the White City, correctly points out that the building techniques developed during the construction of the many buildings of the fair were entirely modern, even if they were adorned in a way Sullivan found aesthetically distasteful.
Frank Lloyd Wright's Prairie School influenced both building design and the design of furnishings. In the early half of the 20th century, popular residential neighborhoods were developed with Chicago Bungalow style houses, many of which still exist. The two-flat apartment building, along with the larger three- and six-flat buildings, make up 30% of Chicago's housing stock. A two-flat includes two apartments, each of which occupies a full floor, usually with a large bay window and with a grey stone or red brick facade. The apartments typically have the same layout with a large living and dining room area at the front, the kitchen at the back and the bedrooms running down one side of the unit.
Many organizations, notably Preservation Chicago and Landmarks Illinois are devoted to promoting the preservation of historic neighborhoods and buildings in Chicago. Chicago has suffered from the same problems with sinking property values and urban decline as other major cities. Many historic structures have been threatened with demolition.