Gammon made his feature film debut in a bit part in the classic prison drama, "Cool Hand Luke" (1967). From his role as a killer in "Macon County Line" (1973) to a detective in "The McCullochs" (1975) and a bartender in "Any Which Way You Can" (1980), the average-looking, slightly squinty-eyed actor carved a modest niche for himself in a good variety of salty character roles. Along with partner Timothy Scott, Gammon also founded the Met Theater in the early 70s and ran it for more than a decade, winning LA Drama Critics Awards for his direction of "Bus Stop" (1973) and for his performance in "The Dark at the Top of the Stairs" (1974). Acting stints on "Bonanza" and "The Wild Wild West" helped create an impressive resume of TV work and, through the 70s and early 80s, both the roles and the prominence of his programs steadily grew.

While Gammon continued to do fine theater work (as in the New York and L.A. productions of Sam Shepard's "A Lie of the Mind") in the late 80s, the profile of both his feature and TV work rose. One of his best film roles came as the sheriff pursuing an elusive and increasingly legendary "little man" wanted for murder in the fine "The Ballad of Gregorio Cortez" (1983). Gammon has subsequently played supporting roles in such films as "Ironweed" (1987), "Major League" (1989), "Crisscross" (1992) and "Wyatt Earp" (1994), and was especially fine as Horsethief Shorty in "The Milagro Beanfield War" (1988). He also took the plunge into series TV with two interesting if short-lived comedies, "Bagdad Cafe" (1990-91), as the scruffy resident artist Rudy, and "Middle Ages" (1992), as part of the motley crowd of Chicago professionals reassessing their lives at the midway point. He had somewhat better luck when he joined the cast of the CBS cop drama "Nash Bridges" (1996-2001), portraying the title character's father.