I hope, the link isn´t anywhere here already.
The Library of Congress digitized 170.000 pictures, made between 1935 and 1945
by the United States Farm Security Administration and Office of War Information (FSA-OWI). Photogrammar
They shows topics of agriculture, but industry, and there aircraft industry too.
Use the map or the search with tags.
Example for the tag "Bomber": Photogrammar Bomber
Cause they are made on behalf of the government, they are free for everyone.