With an interesting answer:
Yes, “Lord of the Rings” was at one time in the public domain in the U.S.
Forget date of copyright; that’s the current law. We’re talking about the old law, which was much more restrictive.
LOTR was published in England, so was copyrighted under British law. Before an American publisher was found, copies were imported into the U.S.
Foul!
Under the old copyright law, if you imported a certain number of copies of a foreign-published book into the US, you could not register copyright in the US and the work would fall into the public domain. LOTR went over the limit.
Donald A. Wollheim of Ace Books had been negotiating with Tolkien’s publisher to publish LOTR in the US. They had refused, preferring a classy hardcover edition to Ace’s cheap paperbacks. When Wollheim learned of the loophole, he rushed out LOTR in paperback, uncopyrighted.
The books did fairly well. Wollheim didn’t pay Tolkien a cent. Eventually, SFWA made him a member and forced Wollheim to pay up (Wollheim claimed he always intended to pay, but couldn’t find Tolkien’s address).
Eventually, Tolkien made changes to the books (most obviously, adding the backmatter – maps and glossaries) and was able to copyright that. Ballentine Books got the paperback rights. If you look on the back of the old Ballentine Books paperbacks, you’ll see a notice from Tolkien saying that these are the authorized edition and that you should buy that. The Ace books eventually went off the market.
The interesting legal point is the status of the Ace editions. Usually once something’s PD, it’s PD forever, and LOTR doesn’t have a soundtrack so it can be brought back (like “It’s A Wonderful Life”). It would be a very interesting legal case if someone took the PD text from the Ace books and published it (only in the US, BTW). I don’t know if they can claim copyright infringement, though there may be trademarks involved.