An earlier draft of To Kill a Mockingbird, titled Go Set a Watchman, was controversially released on July 14, 2015. This draft, which was completed in 1957, is set 20 years after the time period depicted in To Kill a Mockingbird but is not a continuation of the narrative. This earlier version of the story follows an adult Scout Finch who travels from New York to visit her father, Atticus Finch, in Maycomb, Alabama, where she is confronted by the intolerance in her community. The Watchman manuscript was believed to have been lost until Lee's lawyer Tonja Carter discovered it; although this claim has been widely disputed. Watchman contains early versions of many of the characters from To Kill a Mockingbird. According to Lee's agent Andrew Nurnberg, Mockingbird was originally intended to be the first book of a trilogy: "They discussed publishing Mockingbird first, Watchman last, and a shorter connecting novel between the two." This assertion has been discredited however by the rare books expert James S. Jaffe, who reviewed the pages at the request of Lee's attorney and found them to be only another draft of "To Kill a Mockingbird". The statement was also contrary to Jonathan Mahler's description of how "Watchman" was seen as just the first draft of "Mockingbird". Instances where many passages overlap between the two books, in some case word for word, also refutes this assertion.

When was Go Set a Watchman introduced to the public?