McVickers Theater, Chicago, Illinois, Sketch

Louis Sullivan was an American architect and theorist who pioneered the modern skyscraper, developing a distinctive ornamental language that integrated geometric and organic forms across cast-iron facades and terra-cotta surfaces. Working primarily in Chicago from the 1880s onward, he designed the Auditorium Building and the Carson, Pirie, Scott store, establishing a vocabulary of vertical emphasis and decorative unity that influenced generations of architects. His essays on architectural form, particularly his dictum that form follows function, articulated a philosophical foundation for modern design that extended beyond building to industrial production and craft.

Boston, MA, USA