Copyright genealogy has always been notoriously difficult. With no single, central registry keeping track of what was copyrighted, whether the appropriate formalities were followed, whether the copyright was renewed, whether the author is alive or dead, whether the copyright was transferred (by assignment, bequest, or otherwise) and to whom, or any of the other factors that might be relevant, it can be almost impossible to determine the copyright status of a given work. (Two good sites that tell you what you need to know are available here and here, but neither they nor anyone else can tell you where to look for all of the necessary information.) Indeed, this "orphan works" problem is so thorny that it took the Copyright Office more than 200 pages to describe it and a proposed solution in a recent report.
Some significant help is now available. The Chronicle of Higher Education reports that Stanford University has created a searchable Copyright Renewal Database, covering renewal registrations of books (but not other works) published in the United States between 1923 and 1963. That's a key period, as books published in the U.S. before 1923 are now in the public domain, and works published in the U.S. after 1963 were (if necessary) automatically renewed.
Many thanks to the Cardinal for this valuable service.