The book shows how segregation harmed blacks in the south more intensely than blacks in the north. This made the southern states more difficult to overcome the Great Depression.
We can arrive at this answer because:
"To kill a mockingbird" shows how segregation was a very violent system that harmed society, especially the black population.
Although both the south and the north of the country were very racist regions and maintained a high segregationist standard, the south was much more imposing in maintaining racial segregation.
Thus, while the black workforce was still considered necessary to overcome the great depression in the north of the country, blacks were heavily excluded from the workforce.
This meant that black people had many economic difficulties and lived a life with many limitations, which kept them as an easy target for racism and prejudice. However, the white population was not enough to reverse the problems with the great depression, becoming a more backward region economically and socially compared to the north of the country.
