John Donovan Cannon's biography begins in his hometown of Salmon, Idaho, where he graduated from high school in 1940. His academic pursuits at the Academy of Dramatic Arts were put on hold due to his wartime military service from 1942 to 1945.
After the war, Cannon returned to New York to complete his training and acting career, appearing on stage in various classical plays, including "The Taming of the Shrew" and "Henry IV". He also made his Broadway debut in "Lysistrata" and "Peer Gynt", although leading roles were scarce for him during this period.
Cannon's career took a turn when he began to frequently appear as a guest star on numerous television episodes. While his film career became somewhat desultory, he did have memorable roles in two notable films: "Society Red" in "Cool Hand Luke" (1967) and "Calhoun" in "Cotton Comes to Harlem" (1970).
Cannon's first television appearance was in a 1958 episode of "The Phil Silvers Show", where he played a poker-hustling master sergeant. His tough screen persona was well-established by the mid-1960s, but he surprisingly played the timid weakling "Lloyd Chandler" in the final episode of "The Fugitive" (1963).
He was at his scene-stealing best in an episode of "The Invaders" (1967),where he portrayed the sympathetic mobster "Peter Kalter". Cannon also had a recurring role as lawman "Harry Briscoe" in the western comedy series "Alias Smith and Jones" (1971),where he delivered enjoyably caustic one-liners.
However, he will arguably be most fondly remembered for his popular portrayal of the perpetually exasperated, choleric, cigar-chewing NYPD Chief of Detectives, "Peter B. Clifford", in "McCloud" (1970-1977).