what is the purpose of the first chapter of the novel?

Overall, the first chapter sets the background for the story and puts us into the mind of Scout, who narrates most of the novel. She lets us see her childhood perspective early on and introduces us to Dill, whose importance fades later in the novel. We also see some of her early setbacks (i.e., her broken arm) and generally gets us to see what her life is like early on.