Gage died of heart failure Oct. 5 at Sherman Oaks Hospital, said her son Rob Kaminer.
She was married at 14 and had her second child by the time she was 16, all forbidden for a pageant contestant. She also told pageant officials she was 21, but she was 18.
"It's both an accomplishment and a tragedy. She had mixed feelings about the whole thing," Kaminer told The Times.
She was born Mary Leona Gage on April 8, 1939, in Longview, Texas. Gage represented Maryland at the Miss USA pageant held in Long Beach in July 1957. In a Times article after losing the title, Gage said she entered the Maryland contest hoping it would lead to work as a model.
"We needed money desperately," she said in 1957. "I didn't expect to win, and when I did I was told I would be sent to Long Beach for the Miss Universe contest," then at the time held immediately after the Miss USA competition, "I went to the sponsor of the Maryland contest and told him I couldn't go because I was married.
"He told me to forget that I told him I was married and to come out here and keep my mouth shut."
Pageant officials in Baltimore denied they'd known she was married.
Her son called it "a cautionary tale."
"She entered the contest because she needed the money," Kaminer said. "She was only 18 years old, and you have men pushing and pulling at you. I definitely know she was influenced by the people around her at the time. It's a very powerful influence."
Gage had lived in Southern California since the 1960s and became extremely private later in life "because she wasn't the person people remembered," her son said. She suffered from chronic obstructive pulmonary disease, a progressive condition that makes it hard to breathe.
Gage made television appearances after losing the title, including a highly rated one on the "Ed Sullivan Show." With the attention came hate mail.
"I think one half of the U.S. hated me," she told the Baltimore Sun in 2005.
Gage's later years were difficult, including several failed marriages.
"When you're 18 years old and you're the most beautiful girl in the room … and then you're 50 and you're on oxygen and you haven't taken the time to develop yourself in other areas, what are you left with?" Kaminer said. His mother was "really preyed on by men from an early age," he said.
In addition to Kaminer, who lives in Scottsdale, Ariz., Gage is survived by two other sons, David Ennis of Tyrone, Ga., and Nicholas Covacevich of Los Angeles; and three grandchildren. Two other children have died.