World War II played a significant role in accelerating and amplifying these trends.
During the war, the United States government invested heavily in the war effort, which led to a massive expansion of the manufacturing industry. This created millions of new jobs, both in the factories themselves and in the supporting industries such as transportation and construction.
The war also had a profound impact on the social structure of the United States. Before the war, the middle class was a relatively small percentage of the population, but it grew rapidly during the war as millions of people moved from rural areas to cities to work in the factories.
The war also helped to break down traditional class barriers, as people from all backgrounds worked together to support the war effort. This helped to create a more egalitarian society, in which people were less likely to be defined by their social class.
Finally, the war led to an increase in the availability of education and healthcare, which helped to improve the standard of living for all Americans.
In conclusion, World War II played a significant role in the creation and expansion of the middle class in the United States. The war created millions of new jobs, helped to break down traditional class barriers, and increased access to education and healthcare. These factors combined to create a more prosperous and egalitarian society.