In industrial cities there were better chance at getting a job. The ethnic neighborhoods were crowded and dirty. Most immigrants lived in areas where other immigrants from the same country emmigrated from. So you had little Italy, Polish Communities, etc.
The use of vertical integration to create momopolies
The two causes of World War 2 were:
(i) Conflict of ideology between Dictatorship and Democracy
(ii) Inefficiency of league of Nations.