To Kill a Mockingbird is told from the perspective of Jean Louise (Scout) Finch as an adult looking back at the events that occurred during her childhood.
In chapter one, however, she shares how old she was when the chain of events began to occur, which coincides with the time that little Dill came to the house. She was almost six years old when the events began to unfold.
When I was almost six and Jem was nearly ten, our summertime boundaries (within calling distance of Calpurnia) were Mrs. Henry Lafayette Dubose's house two doors to the north of us, and the Radley Place three doors to the south. (Chapter 1)
By the end of chapter thirty, Scout is eight years old, but has certainly grown much more psychologically and intellectually over the course of the novel. With Ewell's death, the drama and chaos that came over the once-peaceful town end.