Monroeville is the town where Harper Lee is from, and Truman Capote lived next door to her.
The fictional town of Maycomb is modeled after Monroeville right down to the courthouse where the trial took place (for the film, the courthouse set was a copy of the Monroeville courthouse).
The town has embraced its literary significance. Each year, for the last 20 years, members of the town put on a production of To Kill a Mocking Bird. The first half of the play is a highly compressed version of the first half of the book. The second half is mainly the courtroom scene, played out in the courthouse (the first half is staged outside of the courthouse; during intermission everyone is herded inside). The whole thing is very meta. It's a fictional story, but you get to watch it acted out in the town and building where Lee witnessed events that inspired characters and incidents in the novel. Fact and fiction blur together.
While it was community theater, the actors did a pretty good job. Their southern accents lend a sense of authenticity to the characters -- nobody is faking an accent, this is what the people Lee grew up with sounded like. The director also deserves credit for taking advantage of part of the playing being staged outside. During the scene where Atticus is standing guard at the jail, the director had the mob enter the scene by driving a classic car onto the outdoor set -- the car swung around from down the street and drove through the audience.
Today the courthouse is a museum dedicated to the history of Monroeville, Harper Lee and Truman Capote. From the historic pictures of the town you can see that despite always being very small (a population under than 10,000), its courthouse square was a well landscaped bustling commercial corridor. Today it's mostly baron. All the retail has moved to the outskirts of town where there are a few big box stores, most notably Walmart.
Courthouse pictures: