Before the war women generally worked until they got married. This was especially true for upper and middle class jobs. Many industries prohibited woman from working or hired them on the condition they were single and not planning on getting married. They were even paid lower wages than men because of this.
After the war they were able to keep some of the jobs that they had prior to the war and their involvement in labor unions increased.
The Great Migration also played a role in the transformation of the work force. Over the course of World War 1 around half a million African Americans moved to the North in search of jobs that the war had produced. When the war ended some returned home, but many continued to live in northern states.