Millsaps College

The Library of Congress Classification System

How to read call numbers in an academic library

Libraries use classification systems to organize the books on the shelves. A classification system uses letters and/or numbers (call numbers) to arrange the books so that books on the same topic are together. This arrangement results in "serendipitous browsing:" you find one book in the catalog, go to the shelf, and, an even better book is sitting right next to it.

From the Online Catalog to the Shelf

Libraries in the United States generally use either the Library of Congress Classification System (LC) or the Dewey Decimal Classification System to organize their books. Most academic libraries use LC, and most public libraries and K-12 school libraries use Dewey.

Call number 'LB 2395 .C63 1991' on the spine of a book and in the online catalog

Anatomy of a Library of Congress Call Number

Call number 'LB 2395 .C65 1991' on the spine of a book and in the online catalog

Book title: Uncensored War: The Media and Vietnam
Author: Daniel C. Hallin
Call Number: DS559.46 .H35 1986

The first two lines describe the subject of the book.
DS559.45 = Vietnamese Conflict

The third line often represents the author's last name.
H = Hallin

The last line represents the date of publication.

Tips for Finding Books on the Shelf

Call number 'LB 2395 .C65 1991' on the spine of a book and in the online catalog

Read call numbers line by line.

Read the first line in alphabetical order:
A, B, BF, C, D... L, LA, LB, LC, M, ML...

Read the second line as a whole number:
1, 2, 3, 45, 100, 101, 1000, 2000, 2430...

The third line is a combination of a letter and numbers. Read the letter alphabetically. Read the number as a decimal, eg:
.C65 = .65 .C724 = .724

Some call numbers have more than one combination letter-number line.

The last line is the year the book was published. Read in chronological order:
1985, 1991, 1992...

Here is a shelf of books with the call number order explained.

Ten Library of Congress call numbers in order on a shelf. On the first line, 'LA' before 'LB'.  On the second line, '2327' before '2328'. On the combination letter number line 'B' before 'C'. For the numbers after the letter on the combination line, '.55' before '.554' and '.554' before '.63'.  For the last line, '1987' before '1991'.

*Guide written by the University System of Georgia