John Grannis was born on July 8, 1848, in Claremont, New Hampshire, to Laurens Grannis and Martha Cole. His father was a farmer who owned $3,000 of real estate and $1,000 of personal property by 1860. Grannis grew up and attended school in Claremont. The family moved to Guildhall, Vermont, sometime in the 1860s, and by 1870, Grannis was working as a farm laborer. He lived in his parents’ household until at least 1880. Grannis married Nellie R. Carlton in Lunenburg, Vermont, on December 30, 1891, and their daughter Margery was born around 1893. The family lived in Lancaster, Vermont, and Grannis worked as a farmer. His wife died on February 5, 1910, and Grannis passed away of arteriosclerosis in Guildhall, Vermont on April 23, 1925.