The answer is: Cities
Approximately, around 80% of united states population live in the cities. This happen because most of job opportunities that exist in united states (whether it's art, technology, or manufacturing) are located in the cities.
Because of this, even people who born in rural areas start to move to inner cities in order to find jobs and sustain their living.
Jazz had its biggest moment in the 1920's so that's out. Speakeasies were very famous because cops were always taking these liquor stores down. And of course, flappers were famous at liquor stores and jazz so i believe football is out ;)
Major General Edward Braddock.
