Benjamin Wilson Day was born around 1824 in Ohio to Elam Day and Almira Mansfield. His father was a farmer who owned $6,000 of real estate and $1,042 of personal property by 1860. The family moved throughout Ohio: they lived in Huron County in 1830, Hancock County in 1840, and Liberty in 1850.
He married Emeline Hubbard on April 9, 1846, and they had five children, including Elam, who was born around 1849. By 1850, Day was working as a physician in Liberty, and he owned $350 of real estate. Two decades later, he was a clergyman in Harrison, Ohio, and he owned $2,000 of real estate and $300 of personal property. By 1900, they were living in Findlay, Ohio. He died in 1902.