Works that are considered in the “public domain” may be used (i.e., copied) freely, without fear of infringing on copyright.
The following categories of publications are generally considered to be in the public domain; that is, their use is not protected by copyright law:
- U.S. works published before 1923 are in the public domain;
- works where the creator has expressly disclaimed a copyright interest;
- works created by the federal government, for example, data files from the 1990 Census; and
- works created and published, as a rule of thumb, about a century ago (see below for duration guidelines).
The Sonny Bono Copyright Term Extension Act, signed into law on October 27, 1998, amends the provisions concerning duration of copyright protection. Effective immediately, the terms of copyright are generally extended for an additional 20 years. Specific provisions are as follows:
- For works created after January 1, 1978, copyright protection will endure for the life of the author plus an additional 70 years. In the case of a joint work, the term lasts for 70 years after the last surviving author’s death. For anonymous and pseudonymous works and works made for hire, the term will be 95 years from the year of first publication or 120 years from the year of creation, whichever expires first;
- For works created but not published or registered before January 1, 1978, the term endures for life of the author plus 70 years, but in no case will expire earlier than December 31, 2002. If the work is published before December 31, 2002, the term will not expire before December 31, 2047;
- For pre-1978 works still in their original or renewal term of copyright, the total term is extended to 95 years from the date that copyright was originally secured.
Determining public domain status
Determining if a particular work is in the public domain can be a daunting task. A detailed guide developed by Peter B.Hirtle of Cornell University makes the process considerably easier and may serve as a useful resource: Copyright Term and the Public Domain in the United States.