This was definitely a time of poverty and racial tension - both of which factor into the story as motivating forces. It was also a time in which America had yet to enter WWII but we were (as was Scout) becoming aware of the existence of a man named Adolf Hitler whose persecution of the Jews has become a forefront in our study of history. However, what we often fail to recognize is the fact that, while here in America we did not send people who were different from the norm to the gas chambers, we still persecuted the. There is a definite parallel that can be drawn between Hitler's treatment of the Jews and American society's treatment of African Americans and the mentally handicapped (as represented by Tom, Helen and Boo).
This was also a time when educational theory was beginning to rear its head. As Miss Caroline scolds Scout for not learning to read the right way, we begin to see the rigidity of an education system that does not take individuality into consideration and tries to make all students conform to what ios the norm. Anyone who is ahead of the class (Scout) or behind (as we can assume Boo was) would be seen as a problem, not as a person.
Racial and social segregation and isolation as well as the viewing of those who are different from the norm (middle class and white) are key elements of the time period that factor heavily into the themes and moral lessons that have made this novel a permanent fixture in the literary canon.