In the United States, the presidential library system is a nationwide network of 15 libraries administered by the Office of Presidential Libraries, which is part of the National Archives and Records Administration (NARA). These are repositories for preserving and making available the papers, records, collections and other historical materials of every president of the United States from Herbert Hoover (31st president, 1929–1933) to Barack Obama (44th president, 2009–2017). In addition to the library services, museum exhibitions concerning the presidency are displayed.