At the Library of Congress, Kristi Finefield reminds us of WPA poster art:
Artists working for the Federal Art Project (FAP), a part of the Work Projects Administration (WPA), created thousands of posters between 1936 and 1943. The posters took on all manner of topics: public health and safety, cultural events and exhibitions, education, tourism, and wartime warnings, to name a few. Only a small percentage of those posters survive, and today they continue to deliver their messages with strong graphics and few words.
With that in mind, it seems only fair that I let the posters do the rest of the talking, while I keep mum!
See some examples here: Keep Mum: WPA Posters Do the Talking | Picture This: Library of Congress Prints & Photos.