The United States Copyright Office is a part of the Library of Congress. It keeps records on items for which copyright registration is sought. It also keeps records of transfers of copyrights from one owner to another, liens against copyrights, and renewals of copyrights.
The head of the Copyright Office is the Register of Copyrights, appointed by the Librarian of Congress. The Copyright Office is divided into seven offices: Chief Information Officer, Chief of Operations, General Counsel, Policy and International Affairs, Public Information and Education, Public Records and Repositories, and Registration Policy and Practice. The last is the office that processes copyright registrations.
The Copyright Office has an online database that includes information on new and renewed copyrights filed from January 1, 1978. Information on older copyrights was published in the Catalog of Copyright Entries (CCE). The Indiana University Libraries have a nearly complete set in print of the CCE volumes. All of the volumes of the CCE have been scanned as PDFs. An inventory of those scanned volumes is maintained here by the University of Pennsylvania Library, with a list of links to scans of the volumes.