Simeon Gallup was born in Ledyard, Connecticut, on August 16, 1837, and had several siblings; the family moved to Mystic, Connecticut, just before the outbreak of the Civil War. Dropping out of his studies at Brown University, he enlisted as a corporal in Battery F of the 1st Rhode Island Light Artillery Regiment on October 29, 1861. Gallup served in North Carolina, Virginia, and Maryland until mustered out on October 28, 1864, by which time he had attained the rank of 1st sergeant. After his military service, Gallup returned to Mystic, where he worked as a merchant, music teacher, and bookkeeper, and also published a historical essay about his adopted hometown. In 1872, he married Lillian Taylor; the couple had one child, Dana, born in 1885. Simeon Gallup died on June 21, 1910.