In the 1920's, the migration of rural Americans to cities affected the nation's cities in many ways. The people of the migration wanted jobs, homes, cars to travel to work with, affordable apartments to live in, ethnic restaurants, and ethnic neighborhoods. The cities now had to face the problems of crowded city streets, pollution from the number of cars, noise pollution, the shortage of housing for all the workers, and a method for organizing and orchestrating the changes required. Because so many American now acquired a job in the cities, the wealthy had a hard time finding servants for the country estates, so they also moved to the cities and built the luxury apartment buildings we see in cities like New York.
Don't forget music. Here I am thinking specifically of Chigago and Detroit. When musicians from the southern states move north for jobs, frequently in the auto industry, they brought their musical traditions with them. Up until this point, the blues music of the rural south had been mostly acoustic but when the small farmers and share-croppers of the south move north for factory jobs and bring their guitars with them, they 'plug-in,' and American music is never the same.