O'Sullivan, Timothy H., c.1840–1882, American pioneer photographer, b. New York City. O'Sullivan worked in Matthew Brady's first New York gallery and on the battlefronts of the Civil War. He made photographs for the 40th-parallel surveys (1867–69) and the first underground mine pictures, at the Comstock Lode. Most of his views made for the Wheeler Colorado River expedition were lost fighting the rapids. In 1873, O'Sullivan photographed the ecology and the civilizations of the Arizona and New Mexico deserts. He was appointed chief photographer to the treasury department in 1880.
See biography by J. D. Horan (1966).