Thomas Jefferson Building Aerial by Carol M

The size of libraries in the United States is determined by a number of metrics, including number of holdings (in terms of volumes or titles held), by

circulation Circulation may refer to: Science and technology * Atmospheric circulation, the large-scale movement of air * Circulation (physics), the path integral of the fluid velocity around a closed curve in a fluid flow field * Circulatory system, a bio ...

(i.e., library materials checked out or renewed); or by number of library visits.The Nation's Largest Public Libraries: Home
American Library Association (last accessed December 24, 2018). The largest public library in the United States—and the second largest library in the world—is the Library of Congress in Washington, D.C., which is the ''de facto'' national library of the United States. It holds more than 167 million items, including "more than 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." The largest research library in the United States is the

Harvard Library Harvard Library is the umbrella organization for Harvard University's libraries and services. It is the oldest library system in the United States and both the largest academic library and largest private library in the world. Its collection ...

in Cambridge, Massachusetts.. Comparing the size of

public libraries A public library is a library that is accessible by the general public and is usually funded from public sources, such as taxes. It is operated by librarians and library paraprofessionals, who are also civil servants. There are five fundamenta ...

with research libraries (such as academic libraries) is complicated by the different definition of ''holdings'' or ''volumes'' used. The Association of Research Libraries uses the National Information Standards Organization definition of ''volume'', which is "A single physical unit of any printed,

typewritten A typewriter is a mechanical or electromechanical machine for typing characters. Typically, a typewriter has an array of keys, and each one causes a different single character to be produced on paper by striking an inked ribbon selectively ...

handwritten Handwriting is the writing done with a writing instrument, such as a pen or pencil, in the hand. Handwriting includes both printing and cursive styles and is separate from formal calligraphy or typeface. Because each person's handwriting is u ...

, mimeographed, or processed work, distinguished from other units by a separate binding, encasement, portfolio, or other clear distinction, which has been cataloged, classified, and made ready for use, and which is typically the unit used to charge

transactions."The Nation's Largest Libraries: A Listing By Volumes Held
(ALA Library Fact Sheet Number 22). American Library Association] (October 2012). In contrast, the Public Library Data Service Statistical Report (a publication of the Public Library Association, which is a division of the American Library Association) defines ''holdings'' as "the number of cataloged items (number of items, number of titles) plus paperbacks and videocassettes even if uncataloged."

Largest public libraries systems by total collections

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. "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 The Compact Cassette or Musicassette (MC), also commonly called the tape cassette, cassette tape, audio cassette, or simply tape or cassette, is an analog magnetic tape recording format for audio recording and playback. Invented by Lou Ottens ...

, audioreels,

CD-ROM A CD-ROM (, compact disc read-only memory) is a type of read-only memory consisting of a pre-pressed optical compact disc that contains data. Computers can read—but not write or erase—CD-ROMs. Some CDs, called enhanced CDs, hold both comput ...

s, and talking books) and downloadable units; and "video materials" similarly includes both physical video materials (such as videotape and DVD) and downloadable video files.

Largest research libraries

The Association of Research Libraries (ARL), a consortium of U.S. and Canada research libraries, reports statistical data on its 124 members (of which 114 are academic libraries within universities and 10 are non-academic research libraries). The ten non-university institutions in the ARL are the

Boston Public Library The Boston Public Library is a municipal public library system in Boston, Massachusetts, United States, founded in 1848. The Boston Public Library is also the Library for the Commonwealth (formerly ''library of last recourse'') of the Commonweal ...

National Research Council Canada National Science Library The National Science Library (NSL), formerly known as the Canada Institute for Scientific and Technical Information or CISTI, began in 1917 as the library of the National Research Council of Canada (NRC). NRC is the Government of Canada's premier ...

, Center for Research Libraries, Library of Congress, National Agricultural Library, National Archives, National Library of Medicine,

New York Public Library The New York Public Library (NYPL) is a public library system in New York City. With nearly 53 million items and 92 locations, the New York Public Library is the second largest public library in the United States (behind the Library of Congress ...

New York State Library The New York State Library is a research library in Albany, New York, United States. It was established in 1818 to serve the state government of New York and is part of the New York State Education Department. The library is one of the largest ...

, and Smithsonian Libraries. 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 campus A satellite campus or branch campus or regional campus is a campus of a university or college that is physically at a distance from the original university or college area. This branch campus may be located in a different city, state, or countr ...

es in their reported statistics; others do not.

25 largest research libraries by volumes held

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." Microform, maps, and "electronic serials and other virtual serial volumes" are excluded from the volume count.

25 largest research libraries by titles held

The following are the 25 ARL members with the largest number of titles held, "including catalogued, locally digitized, and licensed" titles. 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 Anglo-Americans are people who are English-speaking inhabitants of Anglo-America. It typically refers to the nations and ethnic groups in the Americas that speak English as a native language, making up the majority of people in the world who spe ...

. A book or serial title may be distinguished from other titles by its unique International Standard Book Number (ISBN) or

International Standard Serial Number An International Standard Serial Number (ISSN) is an eight-digit serial number used to uniquely identify a serial publication, such as a magazine. The ISSN is especially helpful in distinguishing between serials with the same title. ISSNs a ...

(ISSN)." 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.Morris & Roebuck (2018), p. 60.

Footnotes

References