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Library of Congress Classification System: The LC Call Number

A 'How To' guide to the Library of Congress Classification System

Description of the LC System

The majority of books located in the Dean B. Ellis Library are arranged using the Library of Congress classification system.  This system allows books to be arranged by subject into 21 subject classes.  Each book is assigned an alphanumeric call number based on its subject matter. 

The call number acts as a unique identifier for each item (essentially the book's address in the library), and allows it to be placed on shelves near books about or related to the same subject.  Along with allowing you to locate items on a shelf, using Library of Congress call numbers makes it easier for you to browse for materials on a specific topic.

Let's look at a LC call number to see how this classification system works: PN 2287 .L473 A3 2011

This call number is for the book Drama: An Actor's Education by John Lithgow.

PN-   letter line, describes general subject area; alphabetical order

2287 -  number line, narrows subject area; numerical order

.L473 -  cutter line, further narrows subject area OR specifies author; alphabetical then decimal order

A3 - 2nd cutter line (if present) also in alphabetical then decimal order

2011 - year of publication, numerical order

The first letters, "P", represents one of the 21 major divisions listed below.  In this case the main subject is Language and Literature.  Items are shelved by this letter first in alphabetical order.

  • A: General Works
  • B: Philosophy, Psychology, Religion
  • C: Auxiliary Sciences of History
  • D: World History and History or Europe: Europe, Asia, Africa, Australia, etc.
  • E-F: History of the Americas
  • G: Geography, Anthropology, Recreation
  • H: Social Sciences
  • J: Political Sciences
  • K: Law
  • L: Education
  • M: Music and Books on Music
  • N: Fine Arts
  • P: Language and Literature
  • Q: Science
  • R: Medicine
  • S: Agriculture
  • T: Technology
  • U: Military Science
  • V: Naval Science
  • Z: Bibliography, Library Science, Information Resources

The second letter "N" represents a subdivision of the literatures, Literature (General).

The numbers following the letters are classification numbers (in this example the numbers 2287).  In combination with the class and subclass, the classification number further narrows the subject matter.  These are read as whole numbers, so PN2287 would come before PN2300 and after PN5.

The next piece of information, the L473 A3, is called a Cutter Number.  The cutter number usually indicates the author of the work, but can also respresent other information.  The numeric component of a Cutter  Number is always read as a decimal so in this case the L473 is really L.473  So L473 would come after L472 but before L5.

The last piece of the call number is the year of publication.