In 1953 Duke joined Mueller Electric Co., a family-owned manufacturer of insulators, clips, and similar electrical products sold worldwide and founded by his grandfather in 1908. After a series of management positions, Duke was president from 1980 until his retirement in 1986 following the company’s sale.
Duke married Barbara Field in 1957; they had two boys and a girl, owned a condo in Aspen, and threw their lives into developing Playhouse Square, the renovation of four adjacent theaters in downtown Cleveland that was described as the largest renovation project in American theater history.
Barbara died in 1994, and Duke married Anne Smith Wombwell in 1998. She was strongly supportive of the countless charitable, child-welfare and pro bono organizations in which Duke had leadership roles over the decades prior to his passing Aug. 19, 2019.