The collecting of poster stamps was a well established hobby by the time World War I came about so it is not surprising that a set of these stamps was used to promote the United War Work Campaign which took place November 11-18, 1918. These miniature posters, like their larger counterparts, were used to advertise products and to promote causes. The United War Work Campaign was a coordinated effort to raise funds for the seven private "welfare" agencies, including the American Library Association's Library War Service, that supported our armed forces during and after World War I. The goal of the campaign was to raise $170 million, but $205 million was actually raised. ALA received $3.8 million as its share of the campaign. The stamp in the set of poster stamps that featured ALA was based on a full sized poster illustrated by John E. Sheridan. I have Sheridan's full sized "Hey Fellows" poster in my personal collection. The Tutt Library of Colorado College has the Sheridan poster and other ALA WWI posters displayed on its website. Stamp collectors include poster stamps in a category that they call "Cinderellas" or pseudo postage stamps.