Maycomb is the county seat of Maycomb County, Alabama. This makes it a rather appropriate place for such a high-stakes trial; but it also remains a quintessential small, Southern town. Here's the description from the first chapter:
Maycomb was an old town, but it was a tired old town when I first knew it. In rainy weather the streets turned to red slop; grass grew on the sidewalks, the courthouse sagged in the square. Somehow, it was hotter then: a black dog suffered on a summer's day; bony mules hitched to Hoover carts flicked flies in the sweltering shade of the live oaks on the square. Men's stiff collars wilted by nine in the morning. Ladies bathed before noon, after their three-o'clock naps, and by nightfall were like soft teacakes with frostings of sweat and sweet talcum.
People moved slowly then. They ambled across the square, shuffled in and out of the stores around it, took their time about everything. A day was twenty-four hours long but seemed longer. There was no hurry, for there was nowhere to go, nothing to buy and no money to buy it with, nothing to see outside the boundaries of Maycomb County. But it was a time of vague optimism for some of the people: Maycomb County had recently been told that it had nothing to fear but fear itself. p.11
Thus we have a place where no one was rushed, & by extension, no change is rushed. Here, radical ideas are slowly considered, which puts Atticus in a difficult situation in his defense of Tom. He is fighting against a deep-seated racism that will not be easily rooted out. Nearly everyone in town knows everyone else, & if they don't, they certainly gossip like they do. There's much speculation and stereotyping going on amongst the families. Finally, there is a strict social hierarchy, based on both race and class. The Finches are near the top, being both white and well-off financially. Others, like the Cunninghams, are looked down upon for their economic hardships in the Depression. Calpurnia, Tom & Helen Robinson, and others black families are at the bottom of the social ladder in the town, due to the institutionalized racism.
It is here that Scout learns wisdom, maturity, and morality, against the backdrob of a small sleepy town.