The "Golden twenties", as it was named, was an era of economic success that started after the end of WW1, and ended in 1929 with the Wall Street Crash.
In WW1, the USA were the main exporters of armament and other products to the european countries. That situation generated a lot of income for the country.
In addition, the United Kingdom, hit by the consequences of war, lost its position as the world's main power, which was taked by the USA. With this new status the United States begun to control the commerce, using its privileged position.
Whitin the USA, new technologies that increased the industrial production started to be developed, with the increase of job positions as a necessary consequence.
With all the situations described, the United States lived a period of prosperity both in the domestic sphere and in the commercial relationship with other countries.