Home Library Library of Congress Classification System

Library of Congress Classification System

Library of Congress Classification System


The Library of Congress Classification (LLC) is the official classification system developed and used by the Library to classify their extensive collection of books.  There are twenty-one primary classifications and several subclasses for each primary classification.  The classification system was devised by Congressional Librarian Herbert Putnam as a guide unique to the Library but is the standard used by most academic institutions.  
How does the Library of Congress Classification System work?
Books in the LLC are organized by subject matter.  For instance, Fine Arts books are classified as such:
  • Class N – Fine Arts
  • o Subclass N
  • o Subclass NA – Architecture
  • o Subclass NB – Sculpture
  • o Subclass NC – Drawing, Design and Illustration
  • o Subclass ND – Painting
  • o Subclass NE – Print Media
  • o Subclass NK – Decorative arts
  • o Subclass NX – Arts in general
How does this differ from other methods of classification?
The primary alternative to the LLC is the Dewey Decimal System.  The Dewey decimal system uses three digit numbers for specific topics rather than the alphanumeric codes of the LLC.  Academic institutions tend to use the LLC while public libraries tend to use the Dewey Decimal System.
What is easiest method of locating materials in the Library of Congress Catalogue?
The Library of Congress maintains a dedicated website at catalogue.loc.gov with basic and advanced search functions.  The catalogue entries on that website can point to the physical location of the material as well as other relevant information.  Alternatively, there is an Orientation Gallery in the Jefferson Building with attendants that can help visitors locate desired materials.  Bear in mind that visitors and Reader Information Card holders may not remove materials from the Library of Congress premises.
How does one read a Library of Congress Catalogue call number?
Let’s take for example, the following call number, “HD9904.P53 P866 1983” broken into sections:
  • First there are letters that signify the subject 
  • o HD (Industry, Land use and Labor)
  • Then there are numbers after the letters that define the book’s subject 
  • o 9904 (Manufacturing Industries)
  • o P53 (Alpacas)
  • Lastly there is a “cutter number” that identifies the author, organization or title
  • o P866 1983 (Published in Peru, 1983)
This is a general understanding but classifications have slightly different rules and classifications with respect to the subject matter.