The Office of Presidential Libraries, a part of the National Archives and Records Administration, maintains museum libraries that host documents and other materials collected from each presidential administration; a full list of Presidential Libraries and Museums, including links to their websites and online archives, is available on the National Archives' Presidential Libraries website.
The National Archives also maintains a series of guides on how to research presidential materials in these libraries, as well as a list of statutes, regulations, and executive orders affecting Presidential Libraries and presidential records and documents. For a more extensive discussion of Presidential Libraries, see the Congressional Research Service report: The Presidential Libraries Act and the Establishment of Presidential Libraries.