Works in the Public Domain: including works that never were copyrightable, as well as those for which the copyright has expired. It is not always easy to determine if a work is in the public domain. Different works (depending on when they were first published or created) fall under different sections of the copyright law and recent revisions to the law (including the Sonny Bono Copyright Term Extension Act of 1998) have lengthened the term of copyright protection for some works. One sure rule of thumb is that works published before 1923 are in the public domain.

Minnesota State Colleges and Universities' Intellectual Property Coordinators can assist you in making a determination about copyright duration and when and if a work entered the public domain.