The
term of copyright for a particular work depends
on several factors, including whether it has been
published,
and, if so, the date of first publication. As a general
rule, for works created after January 1, 1978 [nineteen
seventy-eight],
copyright protection lasts for the life of the
author plus an additional 70 [seventy] years.
How Long Does Copyright Protection Last?
(FAQ) | U.S. Copyright Office
https://www.copyright.gov/help/faq/faq-duration.html