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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:

A = General works M = Music
B = Philosophy N = Fine Arts
C = History P = Language and Literature
D = History (except America) Q = Science
E-F = American History R = Medicine
G = Geography S = Agriculture
H = Social Sciences T = Technology
J = Political Science U = Military Science
K = Law V = Naval Science
L = Education Z = Bibliography

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

Q = Science
QA = Mathematics
QB = Astronomy
QC = Physics
QD = Chemistry
QE = Geology
QH = Natural History/Biology
QK = Botany
QL = Zoology
QM = Human Anatomy
QP = Physiology
QR = Microbiology

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:

First: alphabetically → Q
Second: numerically → 1
Third: alpha/numeric → M34
Fourth: alpha/numeric → R56 *not always present
Fifth: date/number/volume → no. 100 *not always present

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:

J JA JK JK JK JK JK
1 80 9 84 84 468 468.5
A4 E2 D6 W742 W9 S4 A2
        B214 W57 1998


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

Per Ref Media
HQ HQ HQ
12 1121 1090.3
A6 O47 G38
    1990


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Tue: 7:30 a.m. - 8:00 p.m.
Wed: 7:30 a.m. - 8:00 p.m.
Thu: 7:30 a.m. - 8:00 p.m.
Fri: 7:30 a.m. - 5:00 p.m.
Sat: 12:00 noon - 8:00 p.m.
Sun: CLOSED
For exceptions and full year hours