The only child of a carpenter father and overprotective mother, Shirley Ardell Mason grew up in the 1920s in a strict and religious Minnesota household. Her hometown of Dodge Center, about 75 miles southeast of Minneapolis, numbered about 900 people.
She died a recluse at 75 from breast cancer in Kentucky on Feb. 26, 1998. By then, the once withdrawn and slender woman who studied art at the state college in Mankato had become one of America's most famous psychiatric patients.
Mason was the real person behind the 1970s best seller "Sybil," which sold 6 million copies with its riveting account of an abused woman inhabited by 16 different personalities. Sally Field won an Emmy Award for her 1976 portrayal seen by 20 percent of the nation.
In the process, Mason popularized the condition known as multiple personality disorder — a trendy 1970s diagnosis. The number of cases mushroomed from about 75 to 40,000 after "Sybil" was published.
Since her death, much of her account has been debunked as a fabrication fueled by a patient's desire to please her psychiatrist — plus the runaway train of pop culture and pop psychology success that Mason cashed in on, along with her doctor and the book's author.
The Sybil story included explosive tales of childhood sexual abuse, with details of lesbian orgies and her mother raping her with kitchen utensils. Experts have since determined the worst of the abuse never occurred.
Journalist Debbie Nathan scoured a vast cache of personal medical records unsealed after Mason's death, ranging from tape-recorded psychiatric sessions to elementary school report cards to old diaries.
"I don't know if it was a lie or a hoax or simply an inability to deal with the truth," Nathan told the Star Tribune in 2011 when her book, "Sybil Exposed," came out. (A synthesized version of her findings, published in the New York Times magazine, can be found at tinyurl.com/realSybil.)