History.com: Women of the Wwii Workforce: Photos Show the Real Life Rosie the Riveters

When the United States entered World War II after the 1941 attacks on Pearl Harbor, men shipped overseas by the millions to serve in the war. This left many of the civilian and military jobs on the home front unfilled -- and that's when women stepped in. Before the war, some women worked in traditionally female-dominated positions, such as secretaries, store clerks and receptionists, but were otherwise rarely seen in the work force. With the labor force's high war-time demands, an estimated six million women started working in fields previously closed to them.