Back our girls over there United War Work Campaign
The army hired women to serve as telephone operators overseas, as this poster shows. The United War Work Campaign was a combined effort of several organizations, including the Y.W.C.A., to raise money for the war. World War I was the first time in American history that women were officially part of the military and government agencies. But, while women were being encouraged to serve in the war, women were also protesting for their right to vote.
For more on American women telephone operators check out:
https://www.nsa.gov/Portals/70/documents/about/cryptologic-heritage/hist...
https://www.loc.gov/collections/stars-and-stripes/articles-and-essays/in...
Underwood, Clarence. Back our Girls over there United War Work Campaign. 1918. Color lithograph. Library of Congress: Prints and Photographs Division. http://hdl.loc.gov/loc.pnp/cph.3g07709 (Accessed December 12, 2018).
Public Domain
Public Domain is a copyright term that is often used when talking about copyright for creative works. Under U.S. copyright law, individual items that are in the public domain are items that are no longer protected by copyright law. This means that you do not need to request permission to re-use, re-publish or even change a copy of the item. Items enter the public domain under U.S. copyright law for a number of reasons: the original copyright may have expired; the item was created by the U.S. Federal Government or other governmental entity that views the things it creates as in the public domain; the work was never protected by copyright for some other reason related to how it was produced (for example, it was a speech that wasn't written down or recorded); or the work doesn't have enough originality to make it eligible for copyright protection.