Cornell has graciously published a copyright chart explaining both what is already in the public domain and when works are scheduled to enter the public domain under existing United States law.
Under current copyright law, if someone stumbled across the missing suitcase of Hemingway’s short stories (described in my post below) and his heirs decided — as they surely would — to publish them, how long would the copyright last? Since Hemingway died July 2, 1961, does copyright in any newly discovered work by him run for 70 years from the date of his death — i.e., until July 2, 2031? Or would the lost manuscripts from 1922 fall into the public domain as works published abroad by a U.S. citizen prior to 1923?
The answer is: neither of those. If Hemingway’s lost manuscripts had in fact been “published” in 1922 in the manner in which they ordinarily would have been sold, then they would be in the public domain. However (not to be too didactic), they were lost, and never published, and thus they would still be entitled to copyright protection. But they would actually be entitled to protection until January 1, 2032, as copyrights continue until the end of the year in which they expire.