All works published before 1 January 1926 have now entered the public domain:
1925 was the year of heralded novels by F. Scott Fitzgerald and Virginia Woolf, seminal works by Sinclair Lewis, Franz Kafka, Gertrude Stein, Agatha Christie, Theodore Dreiser, Edith Wharton, Aldous Huxley ... and a banner year for musicians, too. Bessie Smith, Ma Rainey, the Gershwins, Duke Ellington and Fats Waller, among hundreds of others, made important recordings. And 1925 marked the release of canonical movies from silent film comedians Buster Keaton and Harold Lloyd.
As of today, every single one of those works has entered the public domain. "That means that copyright has expired," explains Jennifer Jenkins, a law professor at Duke University who directs its Center for the Study of the Public Domain. "And all of the works are free for anyone to use, reuse, build upon for anyone — without paying a fee."
On January 1 every year, a new batch of published works is liberated from the constraints of copyright. (For a long time, copyright expired after 75 years, but in 1998, Congress extended the date of copyright expiration for works published between 1923 and 1977 to 95 years.) It's difficult to overstate the importance of having work in the public domain. For example, can you imagine the holidays without It's A Wonderful Life? That movie happened to be unprotected by copyright, so it was able to be shown — a lot — for free, contributing to its establishment as an American Christmas classic.
In an article about this year's Public Domain Day, Jenkins discusses everything from the changes in length of copyright to a fascinating story about the copyright of Hitler's Mein Kampf, which also enters the public domain this year. (A dizzyingly exhaustive list of works from 1925 now in the public domain can be found here.)
I will once again raise my objections to the Mickey Mouse Preservation Act of 1998. The Constitution allows for "limited" protections; 75 years is quite enough, thank you.