What do characters and events reveal about Maycomb’s culture?

Are you referring to the prevailing theme of racism?

yes

Obviously, racism is a major theme of the novel. During the Depression era, blacks were still highly subjugated members of society. Blacks were not permitted to commingle with whites in public settings, as exemplified in the courthouse physical separation of races and in the clearly distinct black and white areas of town. Moreover, things like intermarriage were almost unheard of, and sorely looked down upon.

Throughout the novel, Scout explores the differences between black people and white people. She and Jem attend church with Calpurnia and Scout truly enjoys the experience. Afterwards, she asks Calpurnia if she might be able to visit her house sometime because she has never seen it. Calpurnia agrees, but the visit is never made, largely because Aunt Alexandra puts a stop to it. Jem, Scout and Dill also sit with the black citizens of the town in the balcony of the court house to observe the trial. In addition, Scout and Dill have a lengthy conversation with Mr. Raymond, a white man who married a black woman and has mixed children. Mr. Raymond reveals that he pretends to be an alcoholic by carrying around a paper bag with a bottle of Coca-Cola inside in order to let the town excuse his choice to marry a black woman.

Tom Robinson is convicted purely because he is a black man and his accuser is white. The evidence is so powerfully in his favor, that race is clearly the single defining factor in the jury's decision. Atticus fights against racism, and a few other townspeople are on his side, including Miss Maudie and Judge Taylor. Jem and Scout also believe in racial equality, but are obviously in the minority. When Atticus loses the trial, he tries to make his children understand that although he lost, he did help move along the cause of ending racism as evidenced by the jury's lengthy deliberation period. Usually, such a trial would be decided immediately.