Copyright & Fair Use: Public Domain

Public Domain
The public domain consists of those works whose copyright protection has expired, as well as those which never had copyright protection in the first place. According to the U.S. Copyright Office, "Works in the public domain may be used freely and without the permission of the former copyright owner." 1  

       Examples include:
       Works published before 1923
       Publications created by the U.S. Government

For works created after January 1, 1978: life of the author plus 70 years 

     For joint works: life of the last surviving author plus 70 years

     For anonymous works, pseudonymous works, and works for hire: 95 years from the year of first publication or  
          120 years from the year of creation, whichever expires first

How long does a copyright last?
The U.S. Copyright Office indicates that "the term of copyright for a particular work depends on several factors, including whether it has been published, and, if so, the date of first publication." 2 Once a copyright expires, the work becomes part of the "Public Domain" and can be used freely.
 

References:

1 U. S. Copyright Office. (2010). Where is the public domain? Retrieved from http://www.copyright.gov/help/faq/faq-definitions.html#public_domain

2 U. S. Copyright Office. (2010). How long does a copyright last? Retrieved from http://www.copyright.gov/help/faq/faq-duration.html#duration

• Digital Copyright Slider 

  To help in determining whether something has become part of the public domain, the American Library Association (ALA) has developed a helpful tool called the "Public Domain Slider" (also known as the Digital Copyright Slider).

• Copyright Term and the Public Domain in the United States 

  ​Another useful resource for making the determination, is this chart entitled "Copyright Term and the Public Domain" developed by Cornell University's Copyright Information Center.

• Copyright Renewal Database 

  Created by Stanford University the "Copyright Renewal Database" helps determine if books published between 1923 and 1963 are in the public domain.

• When U.S. Works Pass into the Public Domain 

  The University of North Carolina shares a chronological chart which describes "When U.S. Works Pass into the Public Domain".