Charles Martin Hall was born to Herman Bassett Hall and Sophronia H. Brooks on December 6, 1863, in Thompson, Ohio. Charles' father, Herman, graduated from Oberlin College in 1847, and studied for three years at the Oberlin Theological Seminary, where he met his future wife, Sophronia Brooks. They married in 1849, and the next ten years were spent in missionary work in Jamaica, where the first five of their eight children were born. They returned to Ohio in 1860, after the outbreak of the Civil War forced the closing of foreign missions. Charles Hall had two brothers and five sisters; one brother died in infancy. One of his sisters was chemist Julia Brainerd Hall (1859–1925), who helped him in his research.