Most good stories start with a fundamental list of ingredients: the initial situation, conflict, complication, climax, suspense, denouement, and conclusion. Great writers sometimes shake up the recipe and add some spice.
Exposition (Initial Situation)
Sweet Home Alabama
Beginning with Jean Louise's return home, the first seven chapters are our exposition. There is little hint as to what might happen on this visit home, but it's obviously going to be an important one. Why else write about it?
These seven chapters also have numerous flashbacks, telling us who Jean Louise is, and a bit about her history. Remember: this book was written before To Kill a Mockingbird. So readers need this context.
Rising Action (Conflict, Complication)
Town Hall or Town Fall?
Chapter 8 is the Citizens' Council meeting, and the beginning of the novel's major conflict. There are hints to it throughout, like Jean Louise learning about the sale of Finch's Landing. We see in the exposition that she doesn't handle change well, and finding out that her father might be a racist is a huge change that she is going to have to deal with. The middle of the book is her working this out in her mind.
Climax (Crisis, Turning Point)
Knock-Down, Drag-Out Fight
Jean Louise and Atticus have a showdown in Chapter 17. It's explosive and dramatic: the explosion of all the feelings that have built up in her for the rest of the book. The turning point here is Jean Louise figuratively and literally turning her back on her father and walking away.
Her relationship to him was hanging on by a thread, and the argument—more specifically the fact that Atticus won't argue—snaps that last thread.
Falling Action
Mansplaining
In Chapter 18, Uncle Jack steps in to smooth things over between Jean Louise and Atticus. He reconnects a few small threads, but lets Jean Louise know that it is up to her to decide when, how, and what kind of bridge to rebuild to get back to her father.
Resolution (Denouement)
Shut Up and Drive
At the very end of the book, Jean Louise and Atticus form a truce. She agrees to drive her arthritis-ridden father, but the book stops before we see how harmonious their relationship will be going forward. Since Jean Louise doesn't hit her head getting in the car, we assume it will be a fairly smooth road ahead of the two of them.