The term provincialism can be defined in several different ways. It can mean narrow-minded, rude or narrow in outlook; it can also refer to the characteristics of a particular region. In either case, provincialism can be found throughout To Kill a Mockingbird.
Aunt Alexandra may be the best example of a provincial character in the novel. She fits both aspects of the definition. She is overly proud of her family heritage (even though one of the Finches that she most admired was apparently mentally unstable), and she believes that her family is a little better than others in Maycomb County. She socializes only with the upper-class townspeople, and views others (such as the Cunninghams) with disdain.
To some degree, Boo Radley's parents also fit this description. Overly religious and unsociable, they rarely mingled with their neighbors and restricted young Boo to the confines of their home so he could no longer associate with the type of people (the Cunninghams) who had led him astray.