The Chris Costner Sizemore Papers span the time period 1952-1989, with the bulk of the papers dating between 1956 and 1979. The collection consists largely of correspondence; diaries and writings by Sizemore; clippings centered on film and book promotions or speaking engagements; printed materials related to her appearances; interviews and documentary materials (including film, video- and audiocassettes); and miscellaneous materials including photographs, legal and financial papers, and a general file. Most items relate to Sizemore's struggle with multiple personality disorder (dissociative identity disorder), both personally through letters, writings, and diaries, and publicly through interviews, documentary media, and clippings. The papers provide an in-depth look into the life of a woman with a rare disorder who later came to clearly articulate her life to the public. She became a mental health advocate in a time when mental illnesses were still kept secret. A biography was written by her doctors in 1957, Corbett Thigpen and Hervey Cleckley, called . It was turned into a film the next year. Under the pseudonym, Evelyn Lancaster, Sizemore co-authored with James Poling in 1958. In 1977 she wrote, under her given name, the autobiography .

The Correspondence Series is arranged chronologically, and consists primarily of incoming letters. Dr. Corbett Thigpen, the doctor to deliver the original diagnosis of multiple personality disorder, is prominent in much of the collection; this particular series plainly documents his relationship to Sizemore during treatment and continuing well into the 1970s. He wrote to Sizemore about his writings, revealing much about the publication of (book), and its subsequent movie release. Other correspondents include other doctors, family members, Sizemore's editors and publishers, and organizations for which she lectured. Thus they help document earlier years, when her identity remained a secret, through its release, and her subsequent public life of art shows, lectures, broadcasts, and appearances, often for mental health organizations.

The Writings Series is comprised primarily of the holograph manuscript, typescript, final galley proofs, and paperback edition of , the memoir written by Sizemore with the help of Elen Patillo. This comprehensive view of the book's publication is represented from handwritten copy to final edition. All other parts of the collection provide the context in which the book was created, including a large amount of correspondence from editors, recordings of family interviews (presumably recorded for ), clippings, and financial papers. Other parts of the Writings Series include some short descriptions of parts of her life and poetry. There are a few writings by others.

There are six diaries in the Diaries Series, kept during certain spans of the 1950s and 1970s. Here Sizemore clearly discloses inner thoughts, which reveal very personal information about enduring mental illness and its effects on her family. The Clippings Series conveys the breadth of the advertising campaign for , as well as clippings regarding Sizemore's books, art shows, articles, and lectures. The Printed Materials Series also includes information on , including newsletters, flyers, book tour itineraries, programs, and a few journal articles about Sizemore and multiple personality disorder. There is also an Interviews and Documentary Materials Series that again reflects the public's interest in her life, as well as her own desire to document and share her experiences in writing, speaking, and art. Included is a documentary film by Dr. Thigpen, and video and audiocassettes of television interviews, other appearances, and of family members discussing a shared past (sound quality of some of the audiocassettes is very poor). The Miscellaneous Series also contains items relating to Sizemore's illness and subsequent writing and speaking career, such as financial and legal papers, medical files, notes from certain personalities, and photographs. Additionally, some materials are housed separately for preservation reasons in an Oversize Materials group.