Other noteworthy designs include those for the the Chicago Historical Society expansion, Federal Reserve Bank Building addition and Northwestern University Law School.
Horn also was a longtime educator at the Illinois Institute of Technology School of Architecture.
He studied under mid-century modernist architect Craig Ellwood but was associated with the "Chicago Seven," which rejected modernism's oppressive institutionalization.
Horn, whose work reflected a context-driven design approach, "was a true artist, all about the pure structure," says Greg Cook, Holabird & Root managing principal. "He was very complex in his designs, he did them all in his head, and they always came out beautiful."