Works in the public domain have no copyright and can be used freely. They include works in which the copyright period has expired, such as most works published in the U.S. before 1924, or works which never had copyright protection, such as many materials published by the U.S. federal government, or works elected to be placed in the public domain through a Creative Commons license. Below is a list of Public Domain resources.
Newspapers published in the United States more than 95 years ago are in the public domain in their entirety.
Chronicling America provides access to U.S. newspapers published from 1789-1963.