Rachel Brown, the 22-year-old daughter of Reverend Jeremiah Brown, is a "pretty, but not beautiful" girl. She is a kind and gentle person who dislikes controversy. Rachel is a second-grade schoolteacher and close friend of Bert Cates. She is a purely fictitious character created by Lawrence and Lee. She has no counterpart in the Scopes trial.
Rachel is a dynamic character, a character that is transformed by her experiences and actions. The audience is first introduced to Rachel as she visits Cates in jail. She is nervous and unsure of herself because she has never been to the jail before and because she knows that her father would disapprove of her visiting Cates. Rachel meets Cates and tries to persuade him to admit that he was wrong to teach evolution to his students. She wants him to be on the "right side of things," the side her father is on, the side of fundamentalism.
Rachel's father, a zealous fundamentalist preacher, raised her, and she learned at a young age to fear her father and any thoughts she ever had that deviated from fundamentalism. For Rachel, it had always been " . . . safer not to think at all." She is confused because she loves Cates who believes in academic freedom, yet academic freedom (freedom of thought) is in opposition to her fundamentalist beliefs (a strict interpretation of the Bible).
Rachel questions her own beliefs as she gains awareness of the respect that Drummond and Hornbeck have for Cates. Later, when her father holds a prayer meeting and prays that Cates be destroyed, Rachel automatically defends Cates, only to have her father call for retribution against her also. Disappointed and disillusioned, Rachel must face the fact that her father and his beliefs — and embarrassingly her own beliefs — are narrow-minded and intolerant.
When Rachel testifies against Cates, the stage directions compare her to Brutus, a character in Shakespeare's Julius Caesar who betrays his friend Caesar. By testifying, Rachel betrays Cates. The situation becomes unbearable for Rachel when she is on the witness stand, and it results in her near breakdown.
After reading On the Origin of Species by Darwin, Rachel admits to Cates and Drummond that she doesn't agree with the theory of evolution but realizes and understands the importance of having the freedom to think. Rachel acts on her newfound awareness by leaving her father and his influence over her. She leaves Hillsboro with Cates.