Shirley Ardell Mason was an American

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 psychiatric patient and commercial artist who was reputed to have multiple personality disorder. Her life was fictionalized in 1973 in the book Sybil

Sybil (book)

Sybil is a 1973 book by Flora Rheta Schreiber about the treatment of Sybil Dorsett for dissociative identity disorder by her psychoanalyst, Cornelia B...

, and two films of the same name were made in 1976 and 2007

Sybil (2007 film)

Sybil is a 2007 American docudrama directed by Joseph Sargent. The teleplay by John Pielmeier is based on the 1973 book of the same name by Flora Rheta Schreiber, which fictionalized the story of Shirley Ardell Mason, who was diagnosed with multiple personality disorder...

. Both the book and the films used the name Sybil Isabel Dorsett to protect Mason's identity, though the 2007 remake stated Mason's name in its conclusion.
Mason was born and raised in Dodge Center, Minnesota

Dodge Center, Minnesota

As of the census of 2000, there were 2,226 people, 824 households, and 588 families residing in the city. The population density was 1,173.8 people per square mile . There were 859 housing units at an average density of 452.9 per square mile...

, the only child of Walter Mason (a carpenter and architect) and Martha Alice "Mattie" Hageman.