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. To determine the length of copyright protection for a particular work, consult chapter 3 of the Copyright Act (title 17 of the United States Code). More information on the term of copyright can be found in Circular 15a, Duration of Copyright, and Circular 1, Copyright Basics.
A public domain work is a creative work that is not protected by copyright and which may be freely used by everyone. Use the Copyright Slider Tool (requires enabling Flash) to determine if a work is still protected by copyright.
Works fall into the public domain for three main reasons:
1. the term of copyright for the work has expired;
2. the author failed to satisfy statutory formalities to perfect the copyright; or
3. the work is a work of the U.S. Government.