The first chapter of the book does an excellent job in setting the tone or atmosphere of the whole book. Here is what Lee says:
A day was twenty-four hours long but seemed longer. There was no hurry, for there was nowhere to go, nothing to buy and no money to buy it with, nothing to see outside the boundaries of Maycomb County.
The tone is that Maycomb is a sleepy town, where everyone knows everyone else, and nothing ever happens. To add to this, things don't change, and people certainly do not change. Things are just the way they are.
As the book progresses, something does happen in Maycomb. There is a trial of a black man, Tom Robinson. He is unjustly accused and found guilty. We would think that people would be in an uproar at this, but Maycomb is Maycomb, calm and nothing ever happens. So, after the death of Tom, things go back to normal. People don't change and just go on with their lives. This is the sad reality of the the town.
What makes people like Atticus and Miss Maudie so heroic is that they know this, but they are willing to try to bring change. This is courage - the ability to see the challenge, even though it is huge, and commit to a task, because it is the right thing to do.