In 1955, Knapp appeared as the controversial outlaw, gunfighter, and marshal
Jim Courtright on the
syndicated anthology series Stories of the Century, starring and narrated by
Jim Davis. Knapp was cast as Tom Dixon, a former outlaw trying to change his life and marry his sweetheart in the 1960 episode, "The Devil's Due", on the syndicated anthology series,
Death Valley Days, hosted by
Stanley Andrews. Knapp's longest-running television roles were between 1965 and 1971 in eleven episodes of
ABC's
The F.B.I., starring
Efrem Zimbalist, Jr. Knapp played different roles on the
crime drama, including five times as agent Noel McDonald. His last appearance in the series was in the role of Lee Amboy in "Superstition Rock" on November 28, 1971. Knapp appeared three times each on
The Roy Rogers Show and
Laramie. In the latter NBC western series starring
John Smith and
Robert Fuller, he was cast as Brodie in "Night of the Quiet Men" (December 22, 1959), as Snow in "The Passing of Kuba Smith" (January 3, 1961), and as Gibbs in "The Last Battleground" (April 16, 1963). In 1959, he starred in the lead "The Frank Butler Story" of the CBS fantasy drama,
The Millionaire. Also that year he played the role of Stuart Baxter in the
Perry Mason episode, "The Case of the Caretaker's Cat". He made two other appearances in different roles in 1963: Charles Lambert in "The Case of the Bluffing Blast", and James Bradisson in "The Case of the Drowsy Mosquito". On December 2, 1960, he guest starred in NBC's
Michael Shayne as Arthur Hudson in the episode "Blood on Biscayne Bay". That same week he played Joe Tydell in "The Cavedivers" of the CBS sea drama
The Aquanauts. Several months earlier, he had played Andy Watson in the episode "Underwater Narcotics" of a similar series, the syndicated
Sea Hunt starring
Lloyd Bridges. Between November 10 and December 13, 1965, he was cast nine times as Ben Olson on the long-running
NBC soap opera,
Days of Our Lives, then in its first season. Between 1962 and 1971, he appeared seven times on
CBS's
western series,
Gunsmoke, his last role as a deputy in "Mirage" on January 11, 1971. Between 1953 and 1955, he appeared five times on NBC's original
Dragnet television series starring
Jack Webb. He appeared on four other occasions in 1967 in the revamped version of the same series, including the premiere episode, "
The LSD Story", in which Knapp portrays a lenient father who wants his son, played by
Michael Burns, released for having used the then experimental drug
LSD. Twice Knapp appeared on the following:
The Public Defender,
Navy Log,
The Silent Service,
Hawaiian Eye,
Bonanza,
The Rat Patrol,
Run for Your Life,
M Squad,
Boots and Saddles,
Lock-Up,
The Invaders, and
Cheyenne. In the latter ABC western series starring
Clint Walker, the first network western to be one hour in length, he played Frank Thorne in "Massacre at Gunsight Pass" (May 1, 1961), and Deputy Rankin in "Wanted for the Murder of Cheyenne Bodie" (December 10, 1962). Knapp appeared on such westerns as
The Rifleman,
Broken Arrow,
The Adventures of Rin Tin Tin,
Frontier Doctor,
Black Saddle,
Casey Jones, and
The Gray Ghost. He appeared in such adventure, mystery, and drama series as
Schlitz Playhouse,
Border Patrol,
Surfside 6,
77 Sunset Strip,
The Man and the Challenge,
Behind Closed Doors,
GE True,
Coronado 9,
Arrest and Trial,
Marcus Welby, M.D.,
Adam-12,
Highway Patrol,
The DuPont Show with June Allyson, and the
Kraft Suspense Theatre. His appearance on the syndicated adventure series,
The Everglades, reunited him with series star Ron Hayes, with whom he had been cast in the film
Gunmen from Laredo. Knapp's last role was in 1975 in the
Eddie Albert/
Robert Wagner CBS drama
Switch, in which he played Lieutenant Stone in the unusually titled episode "Gaffing the Skim". ==Filmography==