White industrialists such as Henry Ford profited massively during the 1920s, as the post-World War I economic boom fueled consumption and mass production just as it had during the Gilded Age following the Civil War.
Another group that profited was stock market speculators and investors. It was difficult to lose during that time period if you knew anything about stock, and if you had money to invest in larger quantities, you could make a fortune. Knowing when to cash out was the trick.
The people who gained the most during the 20's were the business owners. Consumers had money to spend and went looking to spend it on many of the new electronics which became popular during this time. As mentioned above the rich got richer and the working class spent there hard earned checks at the businesses of these wealthy businessmen.
'The Great Migration' of African Americans moving north continued well into the 1920's. Referred to as 'the new Negro' African Americans in places like Chicago and New York did experience cultural, political, and economic freedoms on a scale never before seen. However, it must be noted that even in the 'modern' cities these folks were still subject to discrimination.
The large corporations their major shareholders, as well as the new emerging middle class definitely benefited from the laissez-faire Coolidge administration.
Although the 1920's was a reversal of fortune for the labor unions, it is fair to say that generally speaking working conditions continued to get better. This combined with the new technologies and industries of the time gave way to the first wave of mass consumer goods...and that emerging 'middle class' began to consume!
In addition, one more point although a darker one...with the passage of the Volstead Act- Prohibition- the bootlegger became extremely prosperous in America during the 1920's.
I would say that the Americans who gained the most from the economic prosperity of the 1920s were those who had the most resources. By that, I mean that people who were already pretty well off were helped most.
When I say well-off, I am talking about having either A) a decent amount of money or B) a good level of education. For people like these, there were many more opportunities at this time. You could, for example, make a good living in one of the many new white collar jobs with the growing corporations.
By contrast, the unskilled and uneducated didn't benefit much (if at all) as farming became less profitable and as union membership declined.
The 1920s was a decade when the economy of America grew at a very fast pace and America became the wealthiest country in the World. As people consumed, more had to be produced and those working in the factories were ready to buy more with what they had earned. This became a self-sustaining cycle of sorts. And almost everyone in the US seemed to be benefiting from it.
The group of people who gained the most were those who were already rich. They were the ones who opened the new factories and catered to the market of consumers that had been created. In the rural areas this group included those who were rich landlords.
One of the groups of people that were left out in this economic growth were the African Americans who only were allowed to do menial labor for very low wages especially in the southern states. Discrimination and the rise of radical groups like the Ku Klux Klan ensured that African Americans were not made part of the industrial revolution.
A second group left out was the share croppers of the south and mid-Americas. These were people who took land on rent from the rich landlords and tried to cultivate enough to sustain themselves and pay their rents. During this period the prices of agricultural produce dropped as a result of cultivation on a large scale. This ensured that farmers got very little for what they grew and were often evicted from their lands when they failed to earn enough to even pay their rents.