Almost nothing is known about Juliette Peirce's life before she met Charles - not even her name, which is variously given as Juliette Annette Froissy or Juliette Pourtalai. Some historians believe she was French, but others have speculated that she had a Gypsy heritage. On occasion, she claimed to be a Habsburg princess. Scanty facts about her provide only a few possible clues to her past. She spoke French, had the means to support herself, had gynecological illnesses that prevented her from having children, and owned a deck of tarot cards said to have predicted the downfall of Napoleon. She was in New York City at the Hotel Brevoort's New Year's Eve ball in December 1876, where she first met Charles.
Charles Peirce's first wife, Harriet Melusina Fay, had left him in 1875, but he was not divorced from her until 1882. Charles and Juliette became close friends and travel companions, and were likely romantically involved before his divorce was official. This indiscretion is sometimes said to have cost him his career. Charles had a teaching position at Johns Hopkins University. When he was being considered for a permanent post, one of the major American scientists of the day, Simon Newcomb, who apparently did not like Charles, pointed out to a Johns Hopkins trustee that Charles, while an employee of the university, had traveled with a woman to whom he was not married. The ensuing scandal led to Charles' dismissal. His later applications to many universities for teaching posts were all unsuccessful, and in fact he never again held a full-time permanent position anywhere. As a result, Juliette is often blamed for Charles Peirce's failure to reach the eminent social stature his intellect might have commanded.
Charles suffered from trigeminal neuralgia and was manic depressive, which ailments he self-medicated with drugs such as morphine, cocaine, and alcohol. His mental and physical illnesses only worsened with time, and he suffered numerous breakdowns over the course of his life, rendering him increasingly unreliable. His earnings from temporary posts, lectures and articles dwindled, until he and Juliette lived in poverty. At his death he had more than 80,000 pages of unpublished writing.
In her later years, Juliette was described as increasingly frail (she contracted, and eventually died of, consumption). Despite his illnesses and their penury, Juliette apparently never wavered in her support for him, and in her belief in his imminent success. When Charles died in 1914, Juliette was left destitute and alone. She lived another twenty years, dedicated to bringing Charles and his ideas the recognition she believed they deserved. An obituary in Science described her as a "gracious lady" who "lived and passed away...in the distinction of her devotion."
The historical novel The Queen of Cups imagines what Juliette's background and history may have been.