A style of commercial architecture developed by the Chicago School, applied primarily to multistory office buildings and mercantile buildings constructed from about 1875 to 1930. Usually characterized by a tripartite scheme consisting of a base that is one to three stories high, a shaft many stories high; and a cap, usually one to three stories high that tops the structure; a flat roof; an overhanging cornice; unadorned fenestration, most often with large rectangular windows (for example, see Chicago window); bay windows with decorative spandrels, 1. Sometimes called Chicago Commercial style.