Works that are in the public domain are no longer, or never were, under copyright protection. These works can be used and reused however the user wishes; there is no need for seeking permission from the owner. There are four ways that items arrive in the public domain:
Watch this video by the U.S. Copyright Office to learn more about the ways that items enter the public domain.
Works that are in the public domain include:
Even if a work is in the public domain, it is always best to provide citation for the work or provide a record of who created it so that others can find it themselves.