Letters from a Concentration Camp
Clara Estelle Breed, a San Diego children's librarian, was outraged by the WWII era policy of internment for Japanese Americans. In response, she met Japanese American families as they were being sent away by train and distributed stamped and addressed postcards to the children, asking them to write to her and describe life in the camps. Her papers, including cards sent by interned adults and children are now collected at the Japanese American National Museum.
Thanks to amyms on metafilter for this find.