I’ve been doing some reading on copyright and I was shocked to learn more about how long it actually lasts, and how that has changed over time.
All works published in the United States before 1923 are in the public domain. Works published after 1922, 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. link
Category:Author died more than 70 years ago public domain images (wikimedia.org)
…
Question for the Day: How much does the public domain weigh? (lbs)

