Answer: Louis Sullivan, American architect, regarded as the spiritual father of modern American architecture and identified with the aesthetics of early skyscraper. Louis Sullivan, in full Louis Henry Sullivan, (born September 3, 1856, Boston, Massachusetts, U.S.—died April 14, 1924, Chicago, Illinois), American architect, regarded as the spiritual father of modern American architecture and identified with the aesthetics of early skyscraper design. Rather, he believed that architecture must evolve from and express the environment in addition to expressing its particular function and its structural basis. It has been said that Sullivan was the first American architect to think consciously of the relationship between architecture and civilization.