Public domain works must be out of copyright in both the United States and in the source country of the work in order to be hosted on the Commons. If the work is not a U.S. work, the file must have an additional copyright tag indicating the copyright status in the source country. Note: This tag should not be used for sound recordings.PD-1923Public domain in the United States//commons.wikimedia.org/wiki/File:David_Cazes.png
It is an anonymous work or pseudonymous work and 50 years have passed since the date of its publication (or creation, whatever date is the latest)
It is a photographic work, and 50 years have passed since the date of its creation
It is another kind of work, and 50 years have passed since the year of death of the author (or last surviving author)
It is one of "official texts of legislative, administrative or legal nature and their official translations"
Before July 5, 2009, a photographic work was protected for 25 years. Pictures created before July 5, 1984 have already been placed into the public domain.