Horace McMahon dabbled in professional and semi-professional acting while attending Fordham University Law School, continuing to do so while holding down a day job as a newspaper reporter. He made acting his full-time vocation after his first Broadway appearance in 1931. In films from 1937, the growly, jowly MacMahon was initially typed in gangster roles. After scoring a personal success as Lieutenant Monaghan in the 1949 Broadway play Detective Story, MacMahon repeated the role in the 1951 film version -- and thereafter was pigeonholed in "cop" roles. Before beginning his five-year (1958-63) tenure as Lieutenant Mike Parker on the TV series The Naked City, MacMahon had been a semi-regular on Martin Kane (1950, as the newsstand owner who stocked nothing but the sponsor's cigarette) and Make Room for Daddy (1953, as Danny Thomas' agent). His last weekly TV assignment was as Hank McClure, police contact for public relations man Craig Stevens, in the short-lived Mr. Broadway. Having been born near Norwalk, Connecticut, Horace McMahon spent his retirement years in that community with his wife, former actress Louise Campbell.