Red Cross poster circa 1918. Reproduced and available for purchase at The Library of Congress online shop.
As during the War Between the States, knitting played an important role on the home front, providing those left behind with a purpose, and those fighting with a few comforts. The American Red Cross played a vital role in organizing knitting drives across the US.
Below is a link to the socks pattern distributed to volunteer knitters by the Red Cross. This page features a clip of one of the newspapers in which the pattern was originally made available to the public. There are numerous other vintage patterns available on the net.