Not every published work has to be copyrighted, some are not. Works not copyrighted enter the public domain immediately. For copyrighted works, United States copyright law has changed numerous times. Here are brief, general guidelines that cover the majority of published copyright issues:
A printed copyrighted work (book, pamphlet, document) published in the U.S. in 1925, or earlier, is in the public domain.
A work, copyrighted in 1964, or later, is still copyrighted and will remain so for decades to come.
A work copyrighted between 1926 to 1963 (dates inclusive) had to have the copyright renewed in the 28th year after the original copyright date. If the renewal was NOT made, copyright protection expired at the end of the 28th year and cannot be restored. If the copyright was renewed, copyright protection extends for a total of 95 years from the original copyright date, then expires.
There are various ways to check to see if a 1926 - 1963 copyright was renewed, these include:
Note: Other works such as sheet music, sound recordings, and motion pictures have different copyright requirements that are typically more restrictive than those for printed works.