I'll just ignore the opportunity to fight.
Somebody refreshed the Sony Bono Copyright Extension thread (look up top for the link), and I checked to see if WikiPedia had anything. I know it's not the authority, but it has a nice summary for those who don't want to wade through the officialese at the end of Q's link to the US copyright office.

Copyright Term Extension Act

The Copyright Term Extension Act (CTEA) of 1998 extended copyright terms in the United States by 20 years. Since the Copyright Act of 1976, copyright would last for the life of the author plus 50 years, or 75 years for a work of corporate authorship. The Act extended these terms to life of the author plus 70 years and for works of corporate authorship to 120 years after creation or 95 years after publication, whichever endpoint is earlier.[1] Copyright protection for works published prior to January 1, 1978, was increased by 20 years to a total of 95 years from their publication date.

This law, also known as the Sonny Bono Copyright Term Extension Act, Sonny Bono Act, or pejoratively as the Mickey Mouse Protection Act,[2] effectively "froze" the advancement date of the public domain in the United States for works covered by the older fixed term copyright rules. Under this Act, additional works made in 1923 or afterwards that were still protected by copyright in 1998 will not enter the public domain until 2019 or afterward (depending on the date of the product) unless the owner of the copyright releases them into the public domain prior to that or if the copyright gets extended again. Unlike copyright extension legislation in the European Union, the Sonny Bono Act did not revive copyrights that had already expired.

So for a single-authored work composed in 1923 or later, it's the life of the author +95 years.