View images of the American workforce taken during World War II. After the December 7, 1941 Japanese attack on Pearl Harbor, the United States entered into World War II, declaring war on Japan and Germany. War changed the social and economic makeup of the country, as a vast industry needed to rise to meet the needs of military efforts. Since so many men were at war, women left homes to work in factories that built airplanes, ships, bombs, and other military weapons and supplies. Families rationed food, gasoline, and clothing. Industries like automobile manufacturers stopped and diverted their work to the war effort.