J.D. Salinger, in his coming-of-age novel The Catcher in the Rye, repeatedly uses Holden Caufield's red hunting hat as a symbol to show Holden's growth from a young man terrified of becoming an adult to one who begins to accept that he must be able to live in an imperfect world.
In the beginning of the story, Holden introduces the hat as being red and floppy, and he purchases it in a store in New York when the fencing team traveled to the big city. In this part of the story, Holden wants to connect with Allie and does so by wearing on a red hunting hat, which is a connection to his brother's red hair. Another reason Holden bought the hat is to use it as an act of defiance against the fencing team. He doesn't want to seem phony like the rest of the team, so he retaliates by wearing the hat everywhere.
On the other hand, whenever he is around a crowd or he doesn't want to be noticed, Holden takes the hat and shoves it in his pocket. By trying not to be phony, Holden turns out to be the people he hates when he wears the red hunting hat.
Since Holden views the world with such negativity, he feels that he needs to be protected and shielded from its harsh environment. He becomes dependent on the hat to guard him from the cold outside world. When he left the bar, the lady who checked his coat told him to put on the hat because it was cold outside and his hair was all wet. Holden uses the hat for protection against pneumonia when he walks down to the park. In the middle of the story, the hat has grown to be a crutch for Holden.
Towards the end of the novel, Holden starts to lose his mental need for the red hat. He gives it to Phoebe because he wants her to be protected against the adult world, but she returns the hat to Holden, which changes him dramatically. The turning point was scene at the carrousel when Holden is soaking in the rain and he doesn't have a care in the world. Holden lets the world come down on him and he accepts it. Holden now believes that he should stay at home and face his responsibilities.
The hat is something that Holden bought for himself, yet in the end it became a mark of society on Holden because the peculiarity of the hat separated him from others. So, through the symbol of the red hunting hat, J.D. Salinger was able to show how Holden grew and changed throughout the whole novel.