Yale University had posted online 170,000 Library of Congress photographs taken in the United States from 1935 to 1945. The photos come from all over the U.S., and can be accessed with this easy-to-use interactive map. They also used the original captions allowing the viewer to get an honest feel for the time period.
No guarantees but you might find one of your ancestors in this series of photographs. You can start at http://photogrammar.yale.edu/map.
The above photograph is from Caribou, Maine in 1940.