Library of Congress collections contain over 162 million books, periodicals, manuscripts, maps, music, recordings, images, and electronic resources. The LC Catalog contains 17 million records describing these collections. You can search Catalog records by keyword or browse by authors/creators, subjects, names/titles, series/uniform titles, and call numbers. Browse lists also include searching aids such cross-references and scope notes.

Library of Congress cataloging dates back to 1898. The LC Catalog includes many early records (primarily for books and periodicals) created by the Library between 1898 and 1980. These records are gradually being updated to reflect contemporary language and usage. Authors/creators and subjects found on older records often contain the legend “[from old catalog]” to indicate possible deviations from current LC practices. In addition, records for some materials cataloged before 1980 are only available to researchers onsite in the Library’s Main Card Catalog.

Items in the Library’s special collections are generally described as aggregations or archival collections rather than individually identifying each specific item. LC Catalog records for many archival collections are linked to more detailed guides available in Finding Aids Search. Library special format materials are also discoverable via separate expert search systems (such as American Memory, Chronicling America, the Performing Arts Encyclopedia, and the Prints and Photographs Online Catalog) that are gradually being replaced by the single search available from Library of Congress Home. Databases, ejournals, and ebooks that are available to patrons onsite (including items found in fee-based online services) can be located through the E-Resources Online Catalog. Primo Central, a web-scale discovery service, offers access to articles, ebooks, and other eresources in selected subscription and free resources available at LC.