Public domain in the United States

Works are in the public domain if they are not covered by intellectual property rights, such as copyright, at all, or if the intellectual property rights to the works has expired.

Congress has restored expired copyrights several times: "After World War I and after World War II, there were special amendments to the Copyright Act to permit for a limited time and under certain conditions the recapture of works that might have fallen into the public domain, principally by aliens of countries with which we had been at war." Works published with notice of copyright or registered in unpublished form in the years 1964 through 1977 automatically had their copyrights renewed for a second term. Works published with notice of copyright or registered in unpublished form on or after January 1, 1923, and prior to January 1, 1964, had to be renewed during the 28th year of their first term of copyright to maintain copyright for a full 95-year term. With the exception of maps, music, and movies, the vast majority of works published in the United States before 1964 were never renewed for a second copyright term.

Works "prepared by an officer or employee of the U.S. government as part of that person's official duties" are automatically in the public domain by law. Examples include military journalism, federal court opinions (but not necessarily state court opinions), congressional committee reports, and census data. However, works created by a contractor for the government are still subject to copyright. Even public domain documents may have their availability limited by laws limiting the spread of classified information.

The claim that "pre-1923 works are in the public domain" is correct only for published works; unpublished works are under federal copyright for at least the life of the author plus 70 years. For a work for hire, the copyright in a work created before 1978, but not theretofore in the public domain or registered for copyright, subsists from January 1, 1978, and endures for a term of 95 years from the year of its first publication, or a term of 120 years from the year of its creation, whichever expires first. If the work was created before 1978 but first published 1978–2002, the federal copyright will not expire before 2047.

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