Dewey Decimal System: The king of library classification
Did you know that Dec. 10 is Dewey Decimal System Day? Me neither.
Born on Dec. 10, 1851, Melvil Dewey is the librarian who invented the Dewey Decimal system of library classification. And in an age of instant Google searches, QR-coded warehouses and robot-assisted sorting, the Dewey Decimal System is still used every day by thousands of libraries and millions of patrons.
But what exactly is the Dewey Decimal Classification System, and why has it stayed the king of library classification in more than 135 countries? In short, the DDC (libraries do love their acronyms) tries to classify all books into ten broad subjects, expanding or contracting based on the specifics of a book, the size of the library and how granular the staff wants to be. The longest known Dewey number, 331.892829225209712743090511, has 27 digits and describes a book about the 2000-2001 Buhler Versatile Inc. strike in Winnipeg, Canada. Riveting, right? That number combines a base for strikes in specific industries (331.8928), tractors (629.2252), a specific locality (Winnipeg) and a date range (2000-2009).
The first version of Dewey was created in 1873 while Melvil was working at Amherst College, and the first pamphlet explaining the system appeared in 1876, titled A Classification and Subject Index for Cataloging and Arranging the Books and Pamphlets of a Library. It was groundbreaking because it did something earlier systems did not. It organized books by subject, allowing similar titles to sit beside each other and making browsing possible.
Before that, books were shelved by the order they were purchased and by their height. It sounds chaotic (and frankly, weird), but since most library collections were not directly accessible to the public, it was not as much of a problem as you might expect. Times were changing, however, and truly public libraries were starting to appear. The first recognized public library in the United States is likely the late 18th century collection Benjamin Franklin gifted to the Town of Franklin. Residents voted to make the books freely available. Public libraries remained relatively rare until Andrew Carnegie funded the construction of more than 2,500 libraries between 1883 and 1929.
Over the years, the Dewey Decimal System has been updated more than 20 times. The world has certainly changed since its conception. When Dewey created it, for example, Religion, the 200s, meant Christian subjects from 200 to 290, with all other religions placed in 291 through 299. That number structure still exists, but now there are far more books in those last ten numbers than Dewey could have envisioned. This is why decimal places exist –– they allow for infinitely more detail. Other areas, such as computer science, did not exist in Dewey’s lifetime, but the system is flexible enough to expand into fields he could never have imagined. In today’s libraries, many of those titles fall into the 000s, the section for science, knowledge and systems.
Of course, libraries also try new and creative ways to help patrons find materials that might fit into several Dewey categories. At Napa County Library, for example, we shelve all our home and garden materials together, so deck construction sits near patio design, and landscaping is next to container gardening. Sometimes this works beautifully. At other times, we are reminded of how simple and complex DDC can be. At one point, we grouped all our wedding books, including photography, cakes, gowns and similar topics, but Pinterest completely upended that market. What used to be hundreds of new wedding titles each year dropped to a trickle, and eventually we dissolved the section and returned the remaining books to their original Dewey homes.
So, I hope you will help celebrate Dewey Decimal System Day this year by visiting the library, searching our catalog for a subject or two, and wandering through the stacks. With luck, you will find the perfect book on your topic, thanks to Melvil Dewey.
Happy librarying.
Contact the author: Anthony.halstead@countyofnapa.org
The Napa Library is open seven days a week:
Monday – Thursday: 9 a.m. to 8 p.m.
Friday and Saturday: 10 a.m. to 6 p.m.
Sunday: 1 p.m. to 5 p.m.
Call the library at (707) 253-4241
Or visit online at www.napalibrary.org
The Yountville Library is open Tuesday – Saturday: 9 a.m. – 5 p.m.
Call the library at (707) 944-1888
Questions or suggestions for your Library Commissioner: myrnadavid2014@gmail.com
Learn more about Friends of the Yountville Library at: yountvillefol@gmail.com
The Calistoga Library is open six days a week:
Monday, Tuesday, Thursday, Friday and Saturday: 9 a.m. to 6 p.m.
Wednesday: 12 to 8 p.m.
Call the library at (707) 942-4833
Or visit online at www.napalibrary.org
The American Canyon Library:
The American Canyon Library is temporarily closed for renovations from Dec. 1, 2025, through Jan. 4, 2026, with a scheduled reopening on Monday, Jan. 5, 2026. During this time, use other Napa County Library branches, have holds mailed to you for free, pause your holds, or change your pickup location to another branch through your online account.
Call the library at (707) 644-1136
Or visit online at www.napalibrary.org
