The Americans who gained the most during the 1920s were those who already had some money. The gains in wealth that came about as stock prices went up, for example, went mainly to those rich enough to put a lot of money into stocks. In addition, the rise of huge companies made a few captains of industry very rich indeed.
On the other hand, most historians argue that farmers and workers were not sharing in the prosperity. The agricultural sector was the weakest sector in the economy. Prices dropped and many small farmers had to get out of farming as competition from larger farms overwhelmed them.
Workers, too, were hurt, according to most historians. The Republican administration of the 1920s was fairly anti-union. During the 1920s, labor union membership dropped dramatically, partly because of anti-union moves by the government. It must be said, however, that wages did go up during this time even if workers in many industries (like mining and textiles) did suffer as technology destroyed jobs and union as unions lost power.
Overall, then, most historians argue that the rich got richer in the 1920s and the farmers and workers either got poorer or did not benefit as much as the rich did.