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How to Read Call Numbers

How to Read Library of Congress Call Numbers

When you find a Library of Congress (LC) call number in your library search, notice that it is written a bit differently than it will appear on the book spine. In the database, it reads straight across. However, on the book spine, it will be broken down into components that make it easier to read.

  • Books are arranged alphabetically. The first letter of an LC call number indicates the general class the call number falls within.
  • Numbers follow the letters. The numbers define the subject of the book.
  • The Cutter Number is the next set of numbers, and it further distinguishes the book. The Cutter Number indicates the author or title of the book.
  • The edition of a volume is the next part of the call number. The year of publication follows the Cutter number to indicate the edition.


    Visual guide showing what order numbers and letters are read in a LC call number.

    (Image from the St. Cloud State University library page)


Here is an example from Search It:

“Noise and Spirit” catalog info with call number outlined

color coded breakdown of call number


Library of Congress Call Numbers on the Shelf

Close up of LC call numbers on books on a shelf highlighting book with call number ML3531 .N65 2003.

Library of Congress Classification

Call numbers group materials on similar subjects together to facilitate browsing. So, if you find one book that closely matches your topic, you will likely find others next to it on the shelf that fit with your research. This does not mean that ALL books on a topic will be in the same section, however. For example, books on "women in politics" might be located under women's studies, political science, history, sociology, and more - all of which are shelved in different areas of the library.

The beginning letters of an LC call number indicate what broad classification your book is in. To get a sense of where books on particular topics are located in the library, click on any of the links below and find the letter on the library map.

A - General Works

B - Philosophy, Psychology, Religion

C - Auxiliary Sciences of History

D - World History

E/F- History of the Americas

G - Geography, Anthropology, Recreation

H - Social Sciences

J - Political Science

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


Z - Bibliography

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