LibGuides: Copyright: Public Domain

Is it in the Public Domain?

Works fall under the public domain through:

expiration of copyright: the copyright has expired.
failure to renew copyright: the owner failed to follow copyright renewal rules.
dedication: the owner deliberately places it in the public domain.
no copyright protection available: copyright law does not protect this type of work.

Chart to Determine Copyright Term and the Public Domain in the United States
© Peter B. Hirtle. Use of this chart is governed by the Creative Commons Attribution 3.0 License.
Stanford University Copyright Renewal Database
If you are trying to ascertain whether a book that could be out of copyright has, in fact, had its copyright status renewed, the Stanford University Copyright Renewal Database allows users to search for information on copyright renewal requests for books published between 1923-1963.
Cornell Copyright Term and the Public Domain in the United States
The Cornell Copyright Term and the Public Domain in the United States web page provides a detailed table of copyright terms depending on date of publication.

No Known Copyright Restrictions

The Commons
Cultural institutions participating Flickr’s“"The Commons," have reasonably concluded that the photographs they share are free of copyright restrictions are invited to share such photograph under the usage guideline called "no known copyright restrictions."

Public Domain Resources

What it is and what it could be - Public Domain Day 2013 entry from Duke Law Center for the study of Public Domain.

The Public Domain Review - a not-for-profit project dedicated to showcasing the most interesting and unusual out-of-copyright works available online.

Public Domain Day - Every year on New Year's Day, due to the expiration of copyright protection terms on works produced by authors who died several decades earlier, thousands of works enter the public domain - that is, their content is no longer owned or controlled by anyone, but it rather becomes a common treasure, available for anyone to freely use for any purpose. Includes yearly lists of authors whose works move into the public domain.

US Gov't works: everything isn't copyright free
Gov't Printing Office and public domain
Harvard Law School Library LibGuide
A wonderful resource curated by Carli Spina of Harvard Law School Library that provides help in locating and correctly attributing Creative Commons and public domain images, audio, and video.