what is the structural purpose of chapter 1?

The first chapter's emphasis on family history and stories within stories describes the rigid social ties that hold society together in the little town of Maycomb, Alabama, and the inescapable links that tie an individual to his or her family or clan. The book opens by mentioning how at age twelve, Jem broke his arm. The narrator notes that the remainder of the book will explain how this injury occurred, and the novel concludes with this event. From the outset, through historical analysis, the novel tries to conclude how "this particular situation" arose.