There's a wee bit more to it than that...Copyright is non-renewable at the 75 year mark and less if not renewed periodically as I understand. So 1944 or so and older are public domain.
"For works published after 1977, the copyright lasts for the life of the author plus 70 years. However, if the work is a work for hire (that is, the work is done in the course of employment or has been specifically commissioned) or is published anonymously or under a pseudonym, the copyright lasts between 95 and 120 years, depending on the date the work is published.
All works published in the United States before 1924 are in the public domain. Works published after 1923, but before 1978 are protected for 95 years from the date of publication. 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 However, even if the author died over 70 years ago, the copyright in an unpublished work lasted until December 31, 2002. And if such a work was published before December 31, 2002, the copyright will last until December 31, 2047.
Is the Work Published?
In the complicated scheme of copyright laws, which law applies to a particular work depends on when that work is published. A work is considered published when the author makes it available to the public on an unrestricted basis. This means that it is possible to distribute or display a work without publishing it if there are significant restrictions placed on what can be done with the work and when it can be shown to others."
https://fairuse.stanford.edu/overview/faqs/copyright-basics/