Library of Congress Call Numbers

The Library of Congress Classification system divides materials into 21 main classes (or broad subjects). These broad subjects are indicated by alphabetically arranged letters:

Combinations of letters and numbers are used to subdivide these broad subject areas. For example:

The Library of Congress call number system uses a combination of letters and numbers to arrange materials on the shelves. With this system, books and other materials are arranged:

The number on the second line is read as a whole number;
The alpha/numeric combinations on the third and fourth lines are read as decimal numbers; i.e., imagine a decimal point at the beginning of the number. Remember this – it’s important!

The following list of call numbers represents a shelf of Political Science books, arranged in the order in which they would appear on a library shelf:

Location or special collection designations may be added at the beginning of a call number. Examples: