Cowpoke, it depends. If the image/photo was created by someone working for the Federal Govt then ALL of those images are in the public domain and free to be used by anyone. (The fed govt specifically covers that in the Copyright Act by disclaiming any ownership rights in any work, created under the authority of the Fed Govt, however the individual States can claim copyright in works they produce.)
What you've got to be careful with is whether these images were marked with a "copyright" notification because they were registered by their owner with the Copyright Office, or whether they were Fed Govt creations. Sometimes it can be difficult to make that distinction.
Muddying the waters even further, if the images were from the 1940's it's quite possible that even if they were "private property" and registered as a copyright back in the day, unless the owner filed an extension/renewal at the end of the original 28 yr time limit in place prior to 1978. As you can do the math, a photo taking during the war, likely required renewal by the author, or assignee of the author, at the latest around 1973 or so.
The 1978 statute removed the renewal requirement. That's why you often see tv shows and movies in the public domain, because the original owners failed to renew the copyrights. My late client Art Clokey, had about 20 Gumby episodes that fell into public domain, due to this reason, even though he retained the rights to most episodes.