Conlon, whose brief movie-acting career included voicing the fawn Faline in "Bambi," died Wednesday of cancer at her home in Ft. Bragg, Calif., said Bruce Lewis, a friend.
At 4, she was cast as Bonnie Blue Butler for her resemblance to her film-screen parents — Vivien Leigh and Clark Gable — but her memories of making the epic 1939 Civil War saga were vague, more like "snapshots," she often said.
She had adored the black Shetland pony that she rode and recalled how perplexed she was when she spotted what looked like a little girl, dressed exactly as she was, smoking a cigarette on the set.
The actor was an adult male, a little person who was her stunt double when Bonnie Blue falls from her pony, which causes her death and a pivotal plot point — Rhett's profound depression.
In the death scene that followed, she couldn't keep her eyelids from fluttering and wore a death mask when Gable picked her up. She was so frightened when the mask was being made, her tears left visible imprints on it, Conlon later said.
She also recalled how director Victor Fleming had lectured her to remember her lines.
He said, "Cammie, I have a daughter your age and all these men here have families, too, that depend on them to work here. They need to feed those children. But if you don't say your lines, they can't work," she told the Santa Rosa Press Democrat in 1998.
Conlon — billed as Cammie King in the movie — said she never flubbed another line.
She fondly referred to Gable as a "father figure" who looked out for her.
"If they were doing a lot of takes of a certain scene, he would say, 'Come on, fellows. Let's wrap it up — the baby is tired,' " she told the Orlando Sentinel in 2003.
As an adult, she appeared regularly with other actors from "Gone With the Wind" at retrospectives and events honoring the movie. In a blog promoting her memoir "Bonnie Blue Butler," Conlon said she was one of 10 surviving cast members.
"Whenever she could, she used her fame to raise money for causes," Lewis said. "She did it in a very light way. She wasn't full of herself at all."
She was born Eleanore Cammack King on Aug. 5, 1934, in Los Angeles. Her parents divorced around the time "Gone With the Wind" came out.
Her mother, Eleanore, was a columnist for the Los Angeles Examiner and in the late 1940s married Herbert Kalmus, a scientist who founded the Technicolor Corp.
Conlon graduated from USC with a bachelor's degree in communications in 1956 and went to work as a production assistant on "Climax!" a CBS-TV anthology series.
Her first husband, with whom she had two children, died of cancer. She later remarried but divorced in 1976.
In 1980, Conlon moved to Northern California and had a long public-relations career that included working for the Mendocino Coast Chamber of Commerce.
After "Gone With the Wind," she had one more role, voicing Faline, who frolics with the title character in another classic, the 1942 Disney film "Bambi."
"All I really remember is crawling around on the floor of…a sound booth. And probably that was to get me to giggle, because that's what I mostly do" as the character, Conlon said in 2005 on National Public Radio.
Cast in another film in the early 1940s, Conlon came down with chicken pox the day shooting was to begin.
"That was the end of my show biz career," she told The Times in 1967, but she later said her mother had wanted her to have a "normal" childhood.
Of her part in one of the greatest films of all time, Conlon liked to say: "I peaked at age 5."
She is survived by her two children, Matthew Ned Conlon of Chicago and Katie Conlon Byrne of Hawaii, and three grandchildren.
A service will be held at 10:30 a.m. Sept. 22 at St. Brendan Church, 310 S. Van Ness Ave., Los Angeles.