One of several nearly identical group portraits taken of a U.S. Army Air Service detachment at Mather Field, California, during World War I. Photographed in shirt-sleeve order with campaign hats set aside, the men represent the mix of young recruits and seasoned personnel who trained at this Sacramento-area airfield in 1918. Multiple exposures such as this one were common practice, ensuring at least one clear print survived for unit records and personal keepsakes. Project: 218714