In early 1942, as the United States became mobilized for war, posters and signs began to appear expressing the national mood and urging the country's energies into war work. One of the earliest of these was this "Remember Dec. 7th!" poster designed by Allen Sandburg and issued by the Office of War Information (OWI). Note that it refers to "Dec. 7th" meaning the 7 December 1941 Japanese attack on Pearl Harbor, Hawaii. Later in the war the slogan changed to "Remember Pearl Harbor".
The poster also features a quotation from Abraham Lincoln's Gettysburg Address: "... we here highly resolve that these dead shall not have died in vain ...".