Materials in the public domain are not protected by copyright and may be freely used in their entirety.
Most federal government publications are in the public domain. Works created prior to 1923 are in the public domain. Works created between 1924 and 1989 may be in the public domain, depending on whether they were registered (when this was still required) and whether their original copyright term was renewed when it expired.
To see when copyright term expires, check:
To see if copyright was renewed or if a specific work passed into the public domain, check:
A work can also be an "orphan work" meaning that it may still be under copyright, yet no rightsholder can be found.
Nothing on this guide is to be construed as legal advice. These pages are intended to provide information and guidance in the application of copyright law and to expand on the University of Missouri System Collected Rules and Regulations.
Thanks to Miller Nichols Library of UMKC for permission to reuse material from their Copyright guide.