Francis Mack was born around 1849 in Indiana to Ransom and Elizabeth Mack. His father was a farmer who owned $300 of personal property by 1860. The family lived in West Van Buren, Indiana, until the 1850s, when they moved to Jackson, Indiana. The 1860 census recorded him in the household of Sarah Watson, a widowed farmer who lived near his parents. He died sometime after 1860.