John H. Spahr was born around 1816 in Pennsylvania to David Spahr and Mary Heilman. He probably grew up in North Middleton, Pennsylvania. He married Mary Cornman on February 4, 1841, and they had at least three children: Jane, born around 1845; Emma, born around 1850; Henrietta, born around 1852; and Eliza, born around 1855. He also helped raise his grandson, William McClellan Spahr, who was born around 1862. They lived in York, Pennsylvania, and Spahr worked as a hotel keeper.
He served as a quartermaster sergeant in Battery A of the 1st Pennsylvania Light Artillery during the Civil War. He returned to York after the war and worked as a painter and tobacconist. By 1870, he owned $500 of personal property, and he employed at least one white domestic servant. In November 1884, while nailing down planks on a new bridge, he accidentally stepped on a plank that had not been nailed down. He fell into the river, and the plank struck him on the head and knocked him unconscious. He never regained consciousness, and he died on November 5, 1884.