Sumner Burnham (1805-1878) was a resident of Harrison, Maine, a town just outside of Portland. He was a devout Baptist and was sympathetic to the anti-slavery movement. According to the 1860 and 1870 censuses, he worked as a farmer. We know from his diaries that he began work in 1864, as a customs inspector and detective in Portland, Maine, where he looked for contraband coming into the ports.
Burnham was born in Otisfield, Maine, to Nathaniel Burnham II and Abigail Scribner. He married Christina Washburn in 1833, and together they had nine children, all born in Harrison, Maine. Of his sons, Otto was rejected for military service for poor health, while Sumner Jr. was accepted and made his way safely through the war.