The Prelinger Archives website can be accessed here: https://archive.org/details/prelinger

Its rights and permissions statement may be found here: https://archive.org/details/prelinger?tab=about

The Prelinger Archives is a collection of films, many of which are in the public domain, from many different sources, including a rich collection of US government films, educational television, home and amateur movies, and libraries and archives.  Founded in 1983, it has been a part of the Library of Congress’ Motion Picture, Broadcasting, and Recorded Sound Division since 2002.  The Prelinger Archives generally offers its footage through a Creative Commons-Public Domain license, although those requiring higher quality footage would need to work with its licensing agent, Getty Images.  Additionally, each individual item is tagged with licensing information, giving its Creative Commons license and any limitations on use.