WW2's iconic "Rosie the Riveter." With so many men drafted into the armed services, US factories--particularly those producing munitions and war equipment and supplies, were desperate for workers, and women entered the work force in "non-feminine jobs" in droves for the first time in history.
The 1940's brought a big change in fashion. Because of WWII, Fabric was rationed. Women's clothing mimicked men's clothing. They were similar to suits with knee length skirts, neutral colors, square shoulders and plain shoes. Most men were sent to war but their attire did not change much from the 1930's. However, after the war, women's fashion consisted of full flared skirts, emphasis on the waist, and pretty shoes. Bolder colors were also used.