Sturdy character actor prolific on stage, screen and TV in both small and prominent supporting roles, most typically as weathered, rustic types ranging from lawmen to bartenders, from cowhands to military men. Gammon began in the entertainment field at age 19 when he got a job operating a camera at a TV station in Orlando, Florida. Community theater work led him to move to Los Angeles in the early 1960s to try his hand professionally, and soon thereafter he made his TV debut, prophetically, in a small guest role on the long-running Western drama series, "Gunsmoke".

Gammon made his feature film