Why were African Americans were able to change the country for themselves and for all of us in the mid-twentieth century? What had changed to make that possible involved a new class structure of the South. The Civil War, by ending slavery, not only disrupted the racial system of the South, but the class system as well. Out of a long struggle, a new class structure was created, based on white supremacy. That class structure was, in turn, undermined by the Depression and World War II, making black intervention possible as it had never been before.