This is where the story begins, and also the base state that gets disrupted and questioned as the story progresses. The place of the Finches in Maycomb, and how their views relate to the views of their fellow townspeople, is what gets complicated and eventually resolved through the plot.
This battle – between Atticus’s desire to give Tom the best defense possible and other people’s desire to preserve the status quo – fuels a lot of the smaller conflicts between Scout and her peers.
The trial makes it obvious that Atticus is right and his opposition is wrong – so it’s up to the jury to side either with justice or with the racist status quo.
The status quo wins. Despite Atticus’s best efforts, and Jem’s belief that the people of Maycomb couldn’t do something so fundamentally wrong as send an innocent man to the electric chair, the jury convicts Tom. Everything in the novel leads to this point, and nothing is the same for the Finches afterwards.
Suspense is often linked with fear, and in this part of the novel both Jem and Scout are very afraid that Mr. Ewell is going to do something to Atticus.
Mr. Ewell finally strikes, ending the suspense, but unexpectedly Atticus is not his victim – he targets Jem and Scout instead, but gets killed in the process.
In a way this is another climax, since the book has been talking about Boo from the first page, and he doesn’t actually appear until almost the end. But it’s also the resolution, as Scout finally leaves behind the fears and fantasies of her childhood in which Boo plays a part, in order to see him as a real person.