Who is the protagonist in To Kill A Mockingbird and why?

The reason Scout is the protagonist in this story is
evidenced by the changes that take place in her life over the two year period the book
covers. She begins as a rather naive little girl who is not familiar with the lifestyles
of those outside her household. Her world is the safe and comfortable confines of her
home and father. She believes her father is a little boring and has few outstanding
traits. She will find that he is the crack shot in Maycomb County and is not afraid of
upholding truth and justice even when his peers do not agree with him. She finds other
lifestyles, like those of the Ewells, the Radleys, Miss Maudie's, are not how she
experienced life sheltered by Calpurnia and her family. As Scout learns, she accepts
changes in her life that are beyond control. She begins  to learn a female's role in
society and how justice is not always just to those of color. Her acceptance of Boo
Radley as a protector, not a gruesome monster, shows her understanding of people
maturing.