Harry Morey Callahan (1912 – 1999) was an American photographer who is considered to be one of the most influential photographers of the twentieth century. He was also one of the few innovators of modern American photography noted as much for his work in color as for his work in black and white. Born in Detroit, Michigan, he started photographing in 1938 as an autodidact. By 1946, he was appointed by László Moholy-Nagy to teach photography at the Institute of Design in Chicago. Callahan retired in 1977, at which time he was teaching at the Rhode Island School of Design.