Commercial style

Chicago's architecture is famous throughout the world and one style is referred to as the Chicago School. Much of its early work is also known as Commercial style. In the history of architecture, the first Chicago School was a school of architects active in Chicago at the turn of the 20th century. They were among the first to promote the new technologies of steel-frame construction in commercial buildings, and developed a spatial aesthetic which co-evolved with, and then came to influence, parallel developments in European Modernism. A "Second Chicago School" later emerged in the 1940s and 1970s which pioneered new building technologies and structural systems such as the tube-frame structure.

While the term "Chicago School" is widely used to describe buildings constructed in the city during the 1880s and 1890s, this term has been disputed by scholars, in particular in reaction to Carl Condit's 1952 book The Chicago School of Architecture. Historians such as H. Allen Brooks, Winston Weisman and Daniel Bluestone have pointed out that the phrase suggests a unified set of aesthetic or conceptual precepts, when, in fact, Chicago buildings of the era displayed a wide variety of styles and techniques. Contemporary publications used the phrase "Commercial Style" to describe the innovative tall buildings of the era rather than proposing any sort of unified "school".

Some of the distinguishing features of the Chicago School are the use of steel-frame buildings with masonry cladding (usually terra cotta), allowing large plate-glass window areas and limiting the amount of exterior ornamentation. Sometimes elements of neoclassical architecture are used in Chicago School skyscrapers. Many Chicago School skyscrapers contain the three parts of a classical column. The lowest floors functions as the base, the middle stories, usually with little ornamental detail, act as the shaft of the column, and the last floor or two, often capped with a cornice and often with more ornamental detail, represent the capital.

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