Fast on the draw, he also was in 'Gunfight at Comanche Creek,' 'Support Your Local Gunfighter' and 'The Fall Guy.'
Cooper died Monday after a long illness in Memphis, Tennessee, his nephew, Pete Searls, told The Hollywood Reporter.
The boyish Cooper also worked opposite Audie Murphy in Gunfight at Comanche Creek (1963) and Arizona Raiders (1965), and stood out in Rebel in Town (1956), Duel at Apache Wells (1957), Waco (1966), Roy Orbison's The Fastest Guitar Alive (1967), Support Your Local Gunfighter (1971) and One More Train to Rob (1971).
He also was on Gunsmoke three times as well as on Bonanza, Tales of Wells Fargo, Wagon Train, The Rifleman, Death Valley Days and a 1961 Civil War-set episode of The Twilight Zone.
"They let me play cowboy, and they paid me [for it]," Cooper recalled in an undated interview filmed for the Museum of Western Film History in Lone Pine, California. "I'd ridden horses, I got my own horse when I was 12. I used to jump him bareback. I didn't know they had stuntmen; I'd watch a movie and then practice on my horse until I could do [the stunt.]"
He said he also practiced his fast draw for 90 minutes a day for four years.
In Johnny Guitar (1954), directed by Nicholas Ray and filmed in Sedona, Arizona, Cooper rode the same horse that carried Alan Ladd in Shane. His character, in a gang with Ernest Borgnine, Royal Dano and Scott Brady, meets his demise at the end of a rope.
Born Sept. 30, 1933, in Hartford, Connecticut, Cooper joined Life With Father on Broadway in March 1942. The classic period comedy ran for more than seven years, long enough for him to play two of the family's four sons, Harlan (for 15 months) and Whitney (for 21 months).
Asked how he got the gig, Cooper said, "I was the right size, I looked right, I was very polite and I knew the whole [script]," he said. "It was that simple."
He acted in more than 3,000 radio shows, attended Columbia University and worked on live television before making his movie debut with an uncredited part in the film noir Side Street (1950), directed by Anthony Mann.
Around a stint in the U.S. Army, he appeared in such other movies as Woman They Almost Lynched (1953), The Outcast (1954), Burt Lancaster's The Rose Tattoo (1955), The Eternal Sea (1955), The Last Command (1955), A Strange Adventure (1956) and Outlaw's Son (1957).
Cooper also appeared four times on Perry Mason and on The Time Tunnel, Adam-12, Mannix, Dallas and Kung Fu: The Legend Continues.
Survivors include his granddaughter, Pamela, and her family; his grandson, Phillip, and his family; his sister, Bunny; and son-in-law Craig.