Public Domain Day, January 1 in the U.S., marks the end of term of copyright protection for all copyrights expiring within the year. For the last 20 years, however, Public Domain Day in the U.S. has been largely uneventful, as there has been an effective freeze on copyright expiration since 1998. January 1, 2019 will be the first Public Domain Day since then that copyrighted works see their expiration and transition into the public domain in the U.S. 

Works first published in the United States in 1923, such as The Great American Novel by William Carlos Williams, are unique in that they were able to ride a “wave” of various term extensions which would see their copyright protection last until 2019. Such works were governed by the 1909 Copyright Act at the time of publication and, if an author complied with the relevant formalities and properly renewed the registration, the total term of copyright protection lasted 56 years. For a work published in 1923, the term of copyright expired in 1979. However, in 1976 Congress revamped the Copyright Act, and with it, added an extra 19 years of protection for copyrighted works in their renewal term as of 1978. This meant that the term of protection for works such as The Great American Novel was extended through 1998.

In 1998, Congress again extended the maximum term of copyright protection, adding an additional 20 years. The Great American Novel, and other works published in 1923, were thus protected through 2019. Works published in 1922 were not subject to this extension and would be allowed to enter the public domain in 1998, hence the twenty-year freeze.
With no bills to further extend copyright term on the horizon, Public Domain Day 2019 will see the U.S. return to celebrating the unofficial holiday with a number of works transitioning into the public domain. Note well, however, that sound recordings published in 1923 were not subject to the federal Copyright Act at the time, and may still be subject to state or common law protection.