With American entry into World War I in April 1917, the country's postal service underwent a number of changes. To accommodate the heavy costs of waging war, the price of a stamp for domestic mail was raised from 2¢ to 3¢, effective November 2, 1917, until July 1, 1919, when the stamps returned to their pre-war rate. Likewise, the rate for postcards was raised from 1¢ to 2¢ during the same time period. World War I also saw the popular rise of picture postcards printed with white borders, thus enabling companies to save money by using less ink.
Changes also came in the carrying of mail during the war, particularly in American cities. Prior to World War I, women had served as mail carriers in some rural communities, but none served in cities. However, with so many American men entering the armed forces during the war, the Post Office Department experimented with appointing women as mail carriers to replace the men. The "experiment" began in December 1917 in eight cities with the largest post offices—by the war’s end, several other cities had also appointed women mail carriers. Most of these women gave up their positions to returning veterans once the war was over.
The postal service also experimented with airmail during the Great War. On May 15, 1918, the first airmail service between New York and Washington, D.C., began. The U.S. Army Signal Corps lent its planes and pilots for the airmail service, recognizing the valuable flying experience that its pilots would gain.
World War I brought other changes to the distribution of mail in the United States. Under the provisions of the Espionage Act of 1917, the Postmaster General could block the distribution of materials in the mail that he felt interfered with the military and/or supported U.S. enemies. In October 1917 the Censorship Board, comprised of the Post Office Department, Departments of Navy and War, the War Trade Board, and the Committee on Public Information, was formed to regulate mail, cable, radio, telegraph, and telephone communications between the United States and foreign nations. Under this board, the Postmaster General was responsible for the regulation and censorship of mail. Items that passed censorship were stamped to indicate so.
World War I also saw the beginnings of the U.S. Army Post Office (APO), which operated independently of the Post Office Department. The establishment of the APO stemmed from the War Department’s reluctance to share the locations of military units with the Post Office Department, which understandably made the department’s job extremely difficult. Additionally, Congress granted Americans serving in the armed forces the right to send personal correspondence free of charge. These items were designated with postal franks—in this case, markings—such as "Nurse's mail," "Officer's mail," and "Soldier's mail."
The selected correspondence in this section comes from the National Postal Museum. Many of these items are written to women from soldiers or vice versa. Additionally, some of the items are connected to women's wartime voluntary organizations, such as the Jewish Welfare Board and the American Red Cross.
Hennen M. Sanford, The Mail of the A.E.F. American Expeditionary Forces (The American Philatelic Society: Maryland, 1940).
Kathryn Burke, "Letter Writing in America: World War I Letters," National Postal Museum.
"Postal History: Airmail," United States Postal Service (PDF).
"Postal History: Women Carriers," United States Postal Service (PDF).
Richard W. Sackett, "The Beginning of the American APO," The American Philatelist 932 (1978): 857-867.
Theo Van Dam, ed., The Postal History of the AEF, 1917-1923 (New York: The War Cover Club, 1990).
"Women in the Postal Service and Philately," National Postal Museum.
"City Carriers, 1917," 1917, Western Newspaper Union photo, collection of the United States Postal Service, "Photo Gallery: People," United States Postal Service History, JPEG file, https://about.usps.com/who-we-are/postal-history/images/people/1917womencarriers.jpg (accessed April 30, 2015).
"WWI sailor's mail free frank on Red Cross postal card," October 10, 1918, Arago: People, Postage & The Post, National Postal Museum.