how long does a renewed copyright last?

[niobium]

how long does a renewed copyright last? Is it another 95 years, or does the timeline of 70 years after the authors death override the term?

[redrun]

Right, a book published today in the US will have copyright protection until 70 years after the author's death. But the US only adopted this law relatively recently, so anything old enough to matter to us will still be under the old rules.

The old rules provide copyright protection for a set number of years from publication, regardless of the author's date of death.
If the author or publisher filed for an extension, the maximum length is 95 calendar years from publication. Given that, we can be absolutely sure that anything published in 1928 and before is now Public Domain in the USA.
For anything more recent, we rely on folks like Project Gutenberg to make sure nobody ever filed that extension.

[niobium]

so is there a quick way to check with a yes or no? I just thought I should ask because of one of the works by Ellsworth Huntington who died in 1947 would normally be over the 70 years since his death to default into public, except that it had been renewed. Is there a way to check when any renewals expire?

[redrun]

No, there isn't an easy way to check for renewals, and no, Ellsworth Huntington's books are not public domain in the US because they were published under the "old rules" I mentioned above. Those do not depend on the author's date of death, only the date of publication.

This is as simple as it gets for US copyright:
Published 1928 or before (as of 2024) -> It's definitely expired.
Published afterwards -> Check if it's on Gutenberg US (gutenberg.org) or HathiTrust as "Public Domain". If not, we can't trust that it's expired.

More info here:
https://wiki.librivox.org/index.php/Copyright_and_Public_Domain#Determining_Public_Domain_Status

[knotyouraveragejo]

Here's a table that summarizes U.S. copyright term under various conditions:

https://guides.library.cornell.edu/copyright/publicdomain

[Beeswaxcandle]

Over on Wikisource we grapple with similar problems and have developed https://en.wikisource.org/wiki/Help:Copyright_renewals to assist. Note the Useful Resources section has links to transcipts of the Copyright Renewals.