Shirley Ardell Mason, aka Sybil, spent her first 26 years in Minnesota, growing up in Dodge Center and graduating in 1949 from the teachers’ college that became Minnesota State, Mankato. (The Minnesota Star Tribune)

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 By then, the once withdrawn and slender woman who studied art at the state college in Mankato had become one of America's most famous psychiatric patients.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.)

Mason spent her first 26 years in Minnesota, graduating in 1949 from the teachers' college that became Minnesota State, Mankato. She apparently suffered a mental breakdown in college, appearing in yearbooks in the early '40s, but not graduating until the end of the decade.

She then moved to Omaha, where she met psychiatrist Cornelia Wilbur — following the doctor to New York in the 1950s. Taking chemistry classes and later teaching art in New York, Mason spent nearly a decade under Wilbur's care. Short-acting barbiturates such as Sodium Pentothal — the so-called truth serum — were staples of their sessions. The drugs were later determined to spark false memories.

In the trove of records kept on her case, Mason actually admitted making up the many personalities.

"I do not really have any multiple personalities," she wrote in a letter to her psychiatrist. "I do not even have a 'double.' … I am all of them. I have been lying in my pretense of them."

Her doctor chalked it up to a defensive ploy to avoid deeper therapy. By then, Dr. Wilbur was giving presentations and the book deal was in the offing.

The psychiatrist grew "very, very attached to the case emotionally and professionally and I don't think she could give it up," Nathan told National Public Radio in 2011.

Mason, meanwhile, realized that if she pushed too hard on the credibility of all the personalities, she'd lose her support network. Dr. Wilbur was giving her up to 18 hours of therapy a week, often at Mason's home. The doctor gave her patient clothing and paid her rent.

With book profits shared among Mason, Wilbur and author Flora Schreiber, the doctor and patient moved to Lexington in the 1970s after Wilbur landed a teaching job at the University of Kentucky.

Mason never married or had children. She eventually moved into Wilbur's Kentucky home to care for her psychiatrist, who began suffering from Parkinson's disease. Wilbur left her patient $25,000 and all "Sybil" royalties after her death in 1992.

Newsweek magazine retraced Mason's Minnesota years in a 1999 story published less than a year after her death. Her parents, Mattie and Walter Mason, were observant Seventh-Day Adventists. Mason's third-grade teacher in Dodge Center, Frances Abbott, was 93 when she told the magazine how Mattie would grab Shirley's hand "in a vise lock'' to cross streets. "Shirley couldn't get free even if she tried."

Another Dodge Center neighbor, Betty Borst Christensen, said Mattie (Hattie in the book) possessed "a witchlike laugh.

"She didn't laugh much, but when she did, it was like a screech. Shirley was very protected. Her mother didn't let her do much."

Dodge Center's population has nearly tripled to more than 2,500 since Mason's days there. But when the book and movie grabbed America's attention in the '70s, townspeople quickly put together the real people behind the made-up names.

Local antique dealer Wendell Nelson told Newsweek in 1999, "Everything just fit — the description of her mother, of the town, of the old brick schoolhouse kitty-corner from her house.''

Curt Brown's tales about Minnesota's history appear each Sunday. Readers can send him suggestions at mnhistory@startribune.com. A collection of columns is in the "Frozen in History" at startribune.com/ebooks.