Has performed at the Steppenwolf Theater in Chicago, Illinois
Played Don Johnson's father in two television productions: The Long Hot Summer (1985) (TV) and "Nash Bridges" (1996), although he was actually less than ten years older than Johnson.
Was very close friends with Timothy Scott. In 1995, the year Scott died, Gammon appeared in "Streets of Laredo" (1995), the sequel to "Lonesome Dove" (1989), in which Scott had appeared.