Duration: How long does a copyright last?
If the work is published after 1977, the copyright will last for the authors life plus another 70 years.
All published works in the US – before 1923 – are already public. Any work published after 1922 and before 1978 is protected for 95 years starting with the publication date.
And, quoting the copyright basics from Standford.edu here (http://fairuse.stanford.edu/overview/faqs/copyright-basics)
“If the work was created, but not published, before 1978, the copyright lasts for the life of the author plus 70 years. However, even if the author died over 70 years ago, the copyright in an unpublished work lasts until December 31, 2002. And if such a work is published before December 31, 2002, the copyright will last until December 31, 2047.”