Write Who You Know: Scout was based on Harper Lee's childhood, Atticus on her lawyer father, Jem on her four-year older brother, and Dill on her childhood friend Truman Capote. Boo Radley was based on one of her neighbors, and Tom Robinson was the amalgam of several cases. Ultimately everyone in the book is based off of someone from Lee's childhood. The townspeople were not amused.
However, the book was Vindicated by History in Monroeville (Lee's hometown). They perform a stage version of it every year with Audience Participation for the courtroom scene: the audience is segregated as they were in the courtroom, and twelve men from the crowd are selected as the jury.
(Fun Fact: The movie adaptation is Superman's favorite movie.)