Mary Leonard (maiden name: Lewis) was born on February 20, 1834, in Wales to John and Sarah Lewis. The family immigrated to America in the 1830s and settled in St. Albans, Ohio. Her father worked as a farmer there, and by 1850, the family owned $1,000 of real estate.
She married Leonard E. Nichols in the 1850s, and they had at least five children: Loanna, born around 1855; Della, born around 1859; Edward, born around 1861; Charles, born around 1863; and Leonard, born around 1877. They lived in St. Albans, and her husband worked as a farmer. By 1860, they owned $1,500 of real estate. A decade later, they owned $11,000 of real estate and $2,000 of personal property. She died in Outville, Ohio, on January 16, 1912.