On what page can the following quote be found in Harper Lee's To Kill a Mockingbird: Boo Radley is a myth to some children.

That exact quote can actually not be found in Harper Lee's To Kill a Mockingbird. In fact, the word myth is only used once towards the end of the book when the children are being followed in the dark of the night by an unknown person. At first, Jem believes they are being followed by Cecil Jacobs as a prank, but as their pursuer continues, Scout begins to wonder "how long [Jem] would try to keep the Cecil myth going" (Ch. 28).  However, we do learn a great deal in the first chapter about the fears neighborhood children have of Boo Radley based on rumors.

In Chapter 1, we learn about Miss Stephanie Crawford's rumors that Arthur (Boo) Radley never leaves his house because his father put him under house arrest due to insanity once Boo stabbed his father in the leg with a pair of scissors. We also learn that Boo's inability to leave his house creates a great deal of fear and suspicion in the minds of Maycomb's citizens. Specifically, Scout narrates that, at one point, "The town was terrorized by a series of morbid nocturnal events," such as the mutilation of pets and chickens, and Maycomb's citizens suspected Boo of the misdeeds. Though the town learned Crazy Addie was the perpetrator, a man who later committed suicide by drowning in Barker's Eddy, many of Maycomb's citizens refused to stop thinking of Boo in a suspicious light.

In this first chapter, the more Dill grows curious about Boo, the more Jem recites other rumors surrounding Boo. For example, Jem tells Dill that Boo only leaves his house when it is pitch dark. Plus, Jem says Miss Stephanie Crawford once saw Boo in the middle of the night staring "straight through the window at her." Jem even goes so far as to give a mythical description of Boo. According to Jem, Boo is "six-and-a-half feet tall," has a "long jagged scar" across his face, "yellow and rotten" teeth, pop eyes, and drool coming out of his mouth. Boo also has bloodstained hands because he feeds mostly on small raw animals, such as squirrels and cats.

Hence, as we can see, Maycomb's citizens, especially the children, have invented many myths about Boo Radley due to the mystery that surrounds him and the Radley family.