Mary Frances Alexander (maiden name: Atwood) was born on July 25, 1834, in Plymouth, Massachusetts, to Thomas Atwood and Hannah Bartlett. Her father was a mariner who later became a clergyman. Mary grew up and attended school in Plymouth. She married William Bemis Alexander there on September 18, 1853, and their daughter Ida was born around 1855.
They moved to Boston sometime in the late 1850s, and her husband worked as a carpenter there. By 1870, they owned $500 of personal property, and they employed at least one white domestic servant. The family moved to Newton, Massachusetts, sometime before 1882, but they returned to Plymouth by 1900. Her husband died of cancer in 1900, and she lived with an adult granddaughter in Plymouth. She died there in 1911.