This article needs to be updated. Please help update this article to reflect recent events or newly available information.(June 2022)
The Thomas Jefferson Building at the Library of Congress in Washington, D.C., the largest library in the United States and second-largest library in the world with over 167 million holdings, including 39 million books and other printed recordings, 14.8 million photographs, 5.5 million maps, 8.1 million pieces of sheet music, and 72 million manuscripts
The largest libraries in the United States is determined by the number of volumes or titles held, by circulation, including library materials checked out or renewed, or by number of library visits.[1] As of 2018, the largest public library in the United States and second-largest library in the world is the Library of Congress in Washington, D.C., the de facto national library of the United States,[2] which holds over 167 million items, including over 39 million books and other printed materials, 3.6 million recordings, 14.8 million photographs, 5.5 million maps, 8.1 million pieces of sheet music, and 72 million manuscripts.[3] The largest research library in the United States, with nearly 20 million holdings, is the Harvard Library at Harvard University in Cambridge, Massachusetts.
The American Library Association has published data on the size of 25 largest public libraries in the United States. These data are from the Institute of Museum and Library Services's Public Libraries Survey (PLS) for fiscal year 2016. The largest public libraries in the U.S. are far larger than the median public library in the country; almost four-fifths of U.S. public libraries serve areas with populations of fewer than 25,000.[1]
"Total collection" consists of print material, electronic books, audio materials, and video materials, each of which is a particular "data element" defined in the PLS. Print materials include printed books, serial music, and maps, including duplicates; electronic books include digital documents include e-books and digitized documents, including duplicates; "audio materials" include both physical audio files (such as cassette tapes, audioreels, CD-ROMs, and talking books) and downloadable units; and "video materials" similarly includes both physical video materials (such as videotape and DVD) and downloadable video files.[5]
The following volume figures for the largest 20 U.S. and Canada research libraries by volume were reported in ARL Statistics, 2020, published in 2022. Some ARL member libraries include the holdings of law libraries, medical libraries, and branch campuses in their reported statistics; others do not.[6]
The following are the 25 ARL members with the largest number of volumes held. ARL uses the ANSI/NISO Z39.7-2004 definition of "volume": "a single physical unit of any printed, typewritten, handwritten, mimeographed, or processed work, distinguished from other units by a separate binding, encasement, portfolio, or other clear distinction, which has been catalogued, classified, and made ready for use."[7] Microform, maps, and "electronic serials and other virtual serial volumes" are excluded from the volume count.[7]
The following are the 25 ARL members with the largest number of titles held, "including catalogued, locally digitized, and licensed" titles.[8] ARL follows the ANSI/NISO Z39.7-2004 definition of "title": "The designation of a separate bibliographic whole, whether issued in one or several volumes...Titles are defined according to the Anglo-American Cataloging Rules. A book or serial title may be distinguished from other titles by its unique International Standard Book Number (ISBN) or International Standard Serial Number (ISSN)."[8] Multiple copies of the same work (for example, subscriptions to the same publication) are counted as a single title, but a serial title available in multiple formats (for example, print and online) are counted once for each available format.[8]
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