Home|WorldCat, the World’s Largest Library Catalog

WorldCat, the World’s Largest Library Catalog

WorldCat, the World's Largest Library CatalogToday’s Follow Friday is about WorldCat, the world’s largest library catalog. It contains records from libraries  all over the world that report their collections using OCLC, the bibliographic network utility. WorldCat used to be available only to libraries who used OCLC, but they’ve opened up the database to everyone in the last few years.

When I first started out working as a professional librarian (roughly the same time the earth’s crust was cooling), reference works were only available in print and catalogs were unique to each library. It seems a trifle unbelievable now, but renowned libraries made their 3×5 card catalogs available to specialty publishers, who in turn made a handsome living printing gigantic multi-volume sets of copies of those card catalogs. If your library wasn’t distinguished enough to warrant a published card catalog, you had to either go or call the library to see if they owned the book you wanted.

The holy grail for many libraries, especially those in geographic consortia, was the union catalog, libraryspeak for a combined library catalog describing the collections of multiple libraries. Union catalogs were published in book format, like the ones mentioned above, and on microform. Begun in the 1950s, the granddaddy of print union catalogs is the National Union Catalog (NUC), a printed catalog of books held by the Library of Congress and other significant American and Canadian research libraries. The advent of networked electronic databases made the union catalog much easier to produce and deliver.

And that brings us back to WorldCat with 2.6 million items and 404,000 records, making it the largest library catalog ever.

The primary way I use WorldCat for genealogical research is to locate libraries with copies of privately published family histories. Where WorldCat really shines is in their search results window. Above is a screenshot of the search results for Rose Mary Goodwin’s 1983 privately published history of my husband’s Curtis line, entitled A Family Called Curtis.

As you can see, WorldCat helpfully orders the search results by location, providing a list of libraries that hold the title and how far they are from my home. (And don’t forget you can double-click on any image in my blog to get a separate, larger view of the image.)

Remember that WorldCat only contains bibliographic records from professionally managed libraries. Local genealogical and historical societies probably haven’t cataloged their collections through OCLC, so their holdings don’t show up in WorldCat. The library of the Southern California Genealogical Society in Burbank also has a copy of Goodwin’s Curtis book, for example, even though it’s not in WorldCat. So consider WorldCat your first library catalog of choice, but don’t forget to check local collections as well.

About the Author:

Nancy Loe has an MA in American History and an MLS in Library Science and Archives. She has appeared on PBS’s American Experience, at Rootstech, SCGS Jamboree, and state and regional genealogy conferences. Her website was featured in Family Tree Magazine's “Social Media Mavericks: 40 to Follow.”


  1. Sassy Jane Genealogy 7 October 2010 at 6:45 PM - Reply

    @Alice – you’re welcome; it’s my pleasure.

    @clairz – I put myself through library school typing card sets for the campus law library. The average used to be eight cards in a card catalog per book on the shelf. But today, virtually every word in a bib record is searchable. It’s amazing to think how much more intellectual access we have now.

  2. clairz 7 October 2010 at 8:30 AM - Reply

    What a fun stroll through library history. When I started my first library job (assistant bookmobile driver!) for a county-wide library system, there was a lady named Grace whose job it was to type up card sets for every book added to the collection. That would be a complete set for the main library, plus a set to go with the book when it went out to the branch. Each set could contain up to 5 cards (kind of limiting, when you think about it)–title, author, shelf list, subject headings, and maybe a series card. That was a lot of typing for poor Grace, and a lot of filing for the rest of us!

    It’s an exciting world now, library- and genealogy-wise! Thank you for the update.

  3. Alice Sneary 6 October 2010 at 2:05 PM - Reply

    Wonderful! Thanks Sassy Jane for posting your wisdom about WorldCat for other genealogists.

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