Very little of Florence Campbell's personal life is documented in surviving sources. Publisher notes describe her, in the language of her own era, as a lifelong mystic of an inquiring and intellectual temperament who devoted years of study to the symbolic meaning of numbers before setting her system down in book form. Her exact birth year has not been established from any source checked for this entry, and this atlas records only what can be confirmed: that she was active as a numerology writer by 1931 and that she died in late 1964.
What survives clearly is the impact of her single major work rather than a documented biography around it, a pattern common among early twentieth century occult writers whose public identity was built almost entirely around one influential text. Your Days Are Numbered went through multiple editions during her lifetime and after, staying in active print use among practicing numerologists well into the twenty first century, longer than almost any other single book from the same generation of American Pythagorean numerology writers.
This pattern, a durable published legacy attached to a nearly undocumented private life, is not unique to Campbell among early twentieth century American occult writers, many of whom wrote under conditions of relative personal privacy even as their books reached wide audiences. Later numerologists writing in the same broad Pythagorean tradition, including Juno Jordan, are by contrast comparatively well documented, making the gap in Campbell's own record a genuine, specific absence rather than a general feature of the field, and one this atlas records honestly rather than filling with invented detail.