The public domain consists of works that are ineligible for copyright protection, works with expired copyrights, or those that have been placed in the public domain by the creator. These materials are owned by no one and are considered public property. As such, they are available for anyone to use without permission.
Just because something is in the public domain doesn't mean you should not cite it. Always give proper credit to your source!
How does one know if something is in the public domain? In the United States, the following are generally in the public domain:
- Works published before 1924 (as of Jan. 2020; in Jan. 2021, this becomes works before 1925)
- Works published between 1924 and 1964 and copyright not renewed
- Works published between 1923 and 1978 without a notice
- Works which did not include a proper copyright notice prior to March 1, 1989.
- Works created by the U.S. government
- Works dedicated to the public domain by their creators
- Works not fixed in a tangible form, such as speeches and lectures (have not been previously written or recorded in any manner)
- Works that do not have sufficient originality, like lists or tables with content from public documents or other common sources.