In the South, Martin Luther King, Jr. dealt with issues of racial discrimination, forced segregation by the police, and legal issues like the abolition of the Jim Crow laws. In the North, he had to deal with economic issues. Poor people were everywhere in the cities and they had no chance of improving their lives. The schools for the poor had low standards and did not provide the good training needed for the chance of finding better jobs. Many of the whites were vying with the blacks for the same kind of jobs.
In the South King dealt primarily with legal issues, such as changing or abolishing Jim Crow laws and police-enforced segregation. In the North he had to deal with economic issues. The cities were filled with poor people who weren't being given a chance to rise out of poverty.
According to his critics, President Roosevelt proposed increasing the number of justices on the Supreme Court because he knew some of them would resign--meaning he could "pack the court".
