Which factor that contributed to the economic growth of the united states in the period from 1865 to 1920 aroused the most opposition?

Industrialization was the factor that contributed to the economic growth of the United states in the period from 1865 to 1920 and it aroused the most opposition. With industrialization came the urge for people to come to the cities for getting work. The people that came to work had to live in a very poor and unhealthy condition.