When you ask a librarian a question...
I am not a fan of J. D. Salinger. I do not think The Catcher in the Rye was the best coming of age book written this century. I also do not think it was groundbreaking simply because the main character cursed incessantly and displayed a rebellious nature in the 1950s, when the book was published.
Salinger was also not a very good person, from all accounts. He fell in love with Oona O'Neill, daughter of playwright Eugene, when she was 16 years young. If you know anything about Salinger, you'll see that he had a lifelong penchant for teenaged girls. Salinger went to war, and O'Neill married Charlie Chaplin. Salinger only found out about it when he read it in the papers. Furious, he sent her a scathing letter imagining what her wedding night was like with a man who was reportedly being treated with monkey glands, the Viagra of the day.
I, of course, want to read that letter. I searched and searched, finally going to The Library of Congress' website. No luck there, either. However, did you know that you can send an email question to a LOC librarian? Brilliant! So, that's what I did. I got the answer today, and it is a GREAT reply!
Dear Ms. Milligan,
While I can find references to these letters in various biographical information sources on Salinger, I have not found the actual letters. I do not think they have been published, nor have I found them online.
In fact, there was a lawsuit by Salinger to block the publication of unpublished letters in the book J.D. Salinger, A Writing Life by Ian Hamilton. Hamilton eventually published In Search of J.D. Salinger. As the Library of Congress remains closed, I do not have access to this book to know if the letters to Oona O'Neill were part of that lawsuit.
I also have not had success locating collections of Oona O'Neill Chaplin's correspondence. You've probably seen this, but here's a video of Annie Chaplin, Oona's daughter, reading one of the letters by Salinger to her.
Again, I've seen various references to Oona Chaplin's will where she requests that all of her writings be destroyed upon her death. I do not know if this happened and whether it included correspondence written to her. Again, I am at a disadvantage because I do not have access to our print collections presently.
The two libraries with the largest collections of Salinger's letters are the Harry Ransom Center at the University of Texas and the Morgan Library and Museum in New York. You may wish to write to them to see if they have the Salinger/O'Neill letters. If not, they may have received this question previously and know where they are located.
Harry Ransom Center https://www.hrc.utexas.edu/
Morgan Library and Museum https://www.themorgan.org/
Both libraries are currently closed; I do not know if they are continuing to answer questions.
I hope that one of these institutions will have the letters you seek or know if they still exist.
Abby Yochelson Reference Specialist English and American Literature Main Reading Room Researcher & Reference Services Division Library of Congress 101 Independence Avenue, SE Washington, DC 20540-4660 202-707-2138
The book nerd in me is extremely pleased by this reply, and much appreciative of the time it took Ms. Yochelson to research my question. Who says libraries are using their usefulness, and librarians are being replaced? NAY!