Widely regarded as the most influential surgeon general in American history and played a crucial role in changing public attitudes about smoking. Dr. Koop had never served in public office when President Ronald Reagan appointed him surgeon general of the United States in 1981. By the time he stepped down in 1989, he had become a household name. He was the only child of John Everett Koop, a banker and descendant of 17th-century Dutch settlers of New York, and the former Helen Apel. He attended Dartmouth College and, after graduating, entered Cornell University Medical College in Manhattan and married Elizabeth Flanagan of New Britain, Conn., a Vassar student. Dr. Koop completed his residency at the University of Pennsylvania Hospital. Dr. Koop’s first wife died in 2007; he is survived by their three children, Allen, Norman and Elizabeth Thompson; eight grandchildren; and his second wife, Cora Hogue, whom he married in 2010.