What is a union catalog?
Union catalogs are used to determine which libraries hold particular items.
The National Union Catalog (NUC) is a record of publications held in more than eleven hundred libraries in the United States and Canada, including the Library of Congress. Major portions of the NUC are published in two principal series: one covering post-1955 publications and the other pre-1956 imprints. Since 1983, the NUC has been issued on microfiche. The NUC, an author catalog, contains some entries for works in the Library's collections that are not listed in its own general catalogs; consequently, it should be consulted in any thorough examination of the Library's resources.
The printed NUC is housed adjacent to the Main Reading Room in the Jefferson Building and around the perimeter of the center room near the Science Reading Room in the Adams Building, fifth floor. The microfiche NUC is available in the Microform Reading Room and at the Business Reference Services desk.
The Chinese, Japanese, and Korean Union Catalogs, and the South Asian and Southeast Asian Union Catalogs are held by the Asian Division. The Near East, Hebrew, and Yiddish Union Catalogs are held by the African and Middle Eastern Division. The Slavic and Cyrillic Union Catalogs are held by the European Division.
Access to the OCLC and RLIN union catalog databases is provided in the Library's reading rooms.