Harry Callahan (1912 - 1999) was one of the most influential photographic artists of the twentieth century. A master of modernist experimentation, Callahan explored a range of subjects - from landscapes to city streets to portraits of his wife - and techniques throughout his career. Beautifully designed and produced, this book focuses on understanding how Callahan worked, both his day-to-day photographic explorations and his resulting fifty-year career in photography. Exploring the rich contents of the Harry Callahan Archive at the Center for Creative Photography, the authors look at how Callahan's choice of subjects and visual ideas emerged from deliberate and improvisational processes, and how such processes might be revealed with archival materials such as negatives, transparencies, proof prints, sequential ordering and variant printings. This close investigation of Callahan's individual and experimental approach to materials in turn leads to a larger consideration of his relationship to seemingly contradictory strains in American visual culture of the twentieth century.