Windom began acting on stage regularly in the 40s as a member of the American Repertory Company. His subsequent Broadway credits include "Androcles and the Lion," "The World of Suzie Wong," and "Come Blow Your Horn." Windom made his feature debut as the prosecuting attorney in "To Kill a Mockingbird" (1962) and went on to alternate between film, TV and theater. His feature credits include "The Detective" (1968) as a closeted, self-hating murderer of gay men, Robert Altman's "Brewster McCloud" (1970), and "Escape From the Planet of the Apes" (1972) as the president. In later years, Windom appeared in supporting roles in two John Hughes comedies, "Planes, Trains, and Automobiles" (1987) and "She's Having a Baby" (1988), as well as the Jodie Foster/Richard Gere drama "Sommersby" (1993).