(1856–1924), American architect, whose brilliant early designs for steel-frame skyscraper construction led to the emergence of the skyscraper as the distinctive American building type. Through his own work, especially his commercial structures, and as the founder of what is now known as the CHICAGO SCHOOL, (q.v.) of architects, he exerted an enormous influence on 20th-century American architecture. His most famous pupil was the architect Frank Lloyd Wright, who acknowledged Sullivan as his master.

The son of a dancing teacher, Sullivan was born in Boston on Sept. 3, 1856. After studying architecture at the Massachusetts Institute of Technology, he spent a year in Paris at the École des Beaux-Arts and in the office of a French architect. Settling in Chicago in 1875, he was employed as a draftsman, then in 1881 formed a partnership with Dankmar Adler (1844–1900). Together they produced more than 100 buildings. Adler secured the clients and handled the engineering and acoustical problems, while Sullivan concerned himself with the architectural designs. One of their earliest and most distinguished joint enterprises was the ten-story Auditorium Building (1886–89) in Chicago. This famous showplace incorporated a hotel, an office building, and a theater renowned for its superb acoustics. The Wainwright Building, also ten stories high, with a metal frame, was completed in 1891 in Saint Louis, Mo. In 1895 the Sullivan-Adler partnership was dissolved, leading to a decline in Sullivan’s practice. The Carson Pirie Scott (originally Schlesinger and Meyer) Department Store, Chicago, regarded by many as Sullivan’s masterpiece, was completed in 1904. His architectural practice declined alarmingly after that; his last buildings are a series of small banks in the Midwest. All are admired for their superb fusion of bold architectural forms with Sullivan’s characteristic sumptuous ornament. Outstanding are the Security Bank (originally National Farmers’ Bank; 1908) in Owatonna, Minn., and the People’s Savings Bank (1911) in Cedar Rapids, Iowa. Concerned with aesthetics as well as being a working architect, he expressed his ideas in lectures and writings, including the classic Autobiography of an Idea (1924, repr. 1956). His famous axiom, “Form follows function,” became the touchstone for many in his profession. Sullivan, however, did not apply it literally. He meant that an architect should consider the purpose of the building as a starting point, not as a rigidly limiting stricture. He himself employed a rich vocabulary of ornament, even on his skyscrapers. He died on April 14, 1924, in Chicago.

See also AMERICAN ART AND ARCHITECTURE,.