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How to: Understand Call Numbers

Libraries use classification systems to organize books and other materials by subject so that they can be found quickly by library users. Each item has a unique "address," or call number, to help you locate it in the library. Call numbers are placed on the spines of books and are included in library catalog records. Books are arranged on the shelves in order by call number.

American University Library uses Library of Congress Classification, which has become the system of choice for many large research libraries. This system uses a combination of letters and numbers to arrange materials by subject area. This makes it easier to browse the shelves for materials that are similar.

The following table lists the major classes of the Library of Congress Classification system:  

A General Works

B Philosophy, Psychology, Religion

C History (General - Civilization, Genealogy)

D  History (General and Old World) 

E History: America

F American History (Local) and Latin American

G Geography, Anthropology, Recreation

H Social Sciences

J Political Science

K Law

L Education

M Music

N Fine Arts

P Language and Literature

Q Science

R Medicine

S Agriculture, Plant and Animal Industry

T Technology

U Military Science

V Naval Science

Z Bibliography and Library Science

If you have questions about call numbers or need assistance locating a book, please ask a reference librarian for assistance.