The author, Harper Lee, grew up (and still lives part-time in) Monroeville, Alabama. Maycomb is patterned after this small county seat in rural southern Alabama. (Truman Capote also spent some of his childhood in Monroeville!)
The trial in the novel is also based on actual events. It is patterned after the famous Scottsboro trials of the 1930's, in which nine African-Americans were tried for raping two white women.
The setting of Maycomb County is like any county. You have your gossips (Miss. Stephany), old wise men (Atticus), and then you have the people that were born on the wrong side of town (Ewells). People like Stephany Crawford murmured under their breath and people like the Ewells boast so loud that Miss. Stephany has something to critisize about. Everybody wanted to be somebody. Even people on the wrong side of the tracks.
This all depends on the type of setting to which you are referring. Do you mean physical setting or social setting. If you are looking for social setting, Scout gives a beautiful description in chapter one of the novel, beginning with "Maycomb was an old town, but it was a tired old town . . ." (Lee 5). The social setting is a bit less flowery. The 1930s in the south were wraught with racism and the Great Depression. The town consists primarily of farmers and a few professionals, such as Atticus. Families in Maycomb who cannot afford to pay for goods often barter with one another. An example of this is Walter Cunningham, Sr. paying Atticus for services rendered with various goods from his farm. Additionally, the town is divided into a "black side" and a "white side." While slavery as an institution no longer exists in this time, institutionalized segregation has created severe racial tensions.