List of the largest libraries in the United States


The size of libraries in the United States is determined by a number of metrics, including number of holdings, by circulation ; or by number of library visits.
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." Other than the Library of Congress, the largest public library in the United States is the New York Public Library, while the largest research library in the United States is the Harvard Library.
Comparing the size of public libraries with research 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, handwritten, 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 circulation transactions." In contrast, the Public Library Data Service Statistical Report defines holdings as "the number of cataloged items plus paperbacks and videocassettes even if uncataloged."

Largest public libraries 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 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 and downloadable units; and "video materials" similarly includes both physical video materials and downloadable video files.
RankLibraryArea servedTotal collection
1New York Public LibraryManhattan, the Bronx, and Staten Island, New York25,271,223
2Public Library of Cincinnati and Hamilton CountyHamilton County, Ohio11,721,430
3Boston Public LibraryBoston, Massachusetts8,197,010
4Los Angeles Public LibraryLos Angeles, California6,735,561
5Chicago Public LibraryChicago, Illinois5,949,251
6County of Los Angeles Public LibraryLos Angeles County, California5,779,843
7Queens Borough Public LibraryQueens, New York5,670,563
8San Diego Public LibrarySan Diego, California5,272,779
9Dallas Public LibraryDallas, Texas5,155,647
10Hennepin County LibraryHennepin County, Minnesota4,895,312
11Dayton Metro LibraryDayton, Ohio4,719,674
12Detroit Public LibraryDetroit, Michigan4,394,193
13King County Library SystemKing County, Washington3,967,872
14Cleveland Public LibraryCleveland, Ohio3,946,416
15Cuyahoga County Public LibraryCuyahoga County, Ohio3,661,264
16Brooklyn Public LibraryBrooklyn, New York3,660,532
17Miami-Dade Public Library SystemMiami-Dade County, Florida3,626,153
18Allen County Public LibraryAllen County, Indiana2,450,882
19Hawaii State Public Library SystemHawaii3,403,577
20City of St. Louis Municipal Library DistrictSt. Louis, Missouri3,281,380
21Broward County Libraries DivisionBroward County, Florida3,194,345
22San Francisco Public LibraryCity and County of San Francisco, California3,122,259
23Houston Public LibraryHouston, Texas3,084,633
24Las Vegas-Clark County Library DistrictClark County, Nevada3,041,019
25Atlanta Fulton Public Library SystemAtlanta, Georgia2,951,414

Largest research libraries

The Association of Research Libraries, a consortium of U.S. and Canada research libraries, reports statistical data on its 124 members. The ten non-university institutions in the ARL are the Boston Public Library, National Research Council Canada National Science Library, Center for Research Libraries, Library of Congress, National Agricultural Library, National Archives, National Library of Medicine, New York Public Library, New York State Library, and Smithsonian Libraries.
The following volume figures for the largest 20 U.S. and Canada research libraries by volume were reported in ARL Statistics, 2015-16, published in 2018. Some ARL member libraries include the holdings of law libraries, medical libraries, and branch campuses 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, but e-book units are included.
RankLibraryInstitutionVolumes
1Harvard LibraryHarvard University20,870,706
2University of Illinois at Urbana–Champaign University LibraryUniversity of Illinois at Urbana–Champaign14,569,260
3University of Toronto LibrariesUniversity of Toronto Libraries14,448,397
4University of Michigan LibraryUniversity of Michigan14,194,430
5Yale University LibraryYale University13,889,206
6Columbia University LibrariesColumbia University13,594,821
7University of California, Los Angeles LibraryUniversity of California, Los Angeles12,421,635
8University of California, Berkeley LibrariesUniversity of California, Berkeley12,022,996
9University of Texas LibrariesUniversity of Texas at Austin11,524,951
10University of Chicago LibraryUniversity of Chicago11,253,997
11Indiana University LibrariesIndiana University10,369,750
12Princeton University LibraryPrinceton University10,336,123
13University of Wisconsin–MadisonUniversity of Wisconsin10,061,485
14Cornell University LibraryCornell University9,575,046
15Ohio State University LibrariesOhio State University9,397,540
16UNC Chapel Hill LibrariesUniversity of North Carolina at Chapel Hill9,197,350
17University of Alberta LibrariesUniversity of Alberta9,095,839
18University of Washington LibrariesUniversity of Washington9,021,092
19Pennsylvania State University LibrariesPennsylvania State University8,068,792
20Duke University LibrariesDuke University8,047,108
21University of Iowa LibrariesUniversity of Iowa7,799,303
22The Penn LibrariesUniversity of Pennsylvania7,778,224
23University of Arizona LibrariesUniversity of Arizona7,467,238
24University of Minnesota LibrariesUniversity of Minnesota7,393,465
25University of Pittsburgh Library SystemUniversity of Pittsburgh7,373,565

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. A book or serial title may be distinguished from other titles by its unique International Standard Book Number or International Standard Serial Number." Multiple copies of the same work are counted as a single title, but a serial title available in multiple formats are counted once for each available format.
RankLibraryInstitutionTitles Held
1Harvard LibraryHarvard University14,852,253
2University of California, Los Angeles LibraryUniversity of California, Los Angeles13,812,990
3Yale University LibraryYale University11,200,907
4University of California, Berkeley LibrariesUniversity of California, Berkeley9,572,771
5Columbia University LibrariesColumbia University9,568,363
6University of Michigan LibraryUniversity of Michigan9,197,263
7University of Illinois at Urbana–Champaign University LibraryUniversity of Illinois at Urbana–Champaign8,857,980
8University of Toronto LibrariesUniversity of Toronto Libraries8,511,629
9University of California, Santa Barbara LibraryUniversity of California, Santa Barbara8,147,213
10University of Wisconsin–MadisonUniversity of Wisconsin8,125,395
11Michigan State University LibrariesMichigan State University7,800,120
12Indiana University LibrariesIndiana University7,784,339
13Princeton University LibraryPrinceton University7,759,990
14Cornell University LibraryCornell University7,571,682
15University of Chicago LibraryUniversity of Chicago7,408,866
16University of Texas LibrariesUniversity of Texas at Austin6,642,492
17Duke University LibrariesDuke University6,348,148
18Pennsylvania State University LibrariesPennsylvania State University6,318,518
19Ohio State University LibrariesOhio State University6,300,022
20University of British Columbia LibraryUniversity of British Columbia6,079,421
21University of Pittsburgh Library SystemUniversity of Pittsburgh6,027,418
22New York University LibrariesNew York University5,945,478
23Northwestern University LibraryNorthwestern University5,919,159
24LSU LibrariesLouisiana State University5,855,226
25University of Iowa LibrariesUniversity of Iowa5,818,670