Specifically in the 1930's
Definition of intolerance
a. Unwilling to tolerate differences in opinions, practices, or beliefs, especially religious beliefs.
b. Opposed to the inclusion or participation of those different from oneself, especially those of a different racial, ethnic, or social background.
c. Unable or unwilling to endure or support
Blacks vs Whites
North vs South
Ku Klux Klan a.k.a. KKK
General 1930 vs general 2013
To Kill A Mockingbird
The setting of TKM is set in the 1930's so based on what I've given you so far, you can see how hostile the US was for blacks back then. It was the Great Depression and many could not find jobs, so many blacks worked as farm hands and maids. The Jim Crow Laws were created to start segregation and whites usually followed them. Mayella Ewell however broke this code and covered her guilt by lying in court.