Frank William Farnum was born on January 24, 1850, in Concord, New Hampshire, to Timothy W. Farnum and Rebecca Bartlett. His father was a bookbinder who owned $1,000 of personal property by 1860. The family lived in Concord until the 1850s, when they moved to Northwood, New Hampshire. He grew up and attended school there, and he completed at least two years of college. By 1870, he was working as a gardener.
He married Cora Lovering around 1885, and their daughter Cora was born around 1891. By 1900, the family was living in Saugus, Massachusetts, and Farnum was working as a “groceryman.” A decade later, he was working as a lithographer. His wife died in Northwood on June 18, 1940. By April 1940, he was living with a niece in Pembroke, New Hampshire. He died of pneumonia in Charlton, Massachusetts, on January 3, 1944.