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Learn to Read a Library of Congress Number

Introduction to Library of Congress Classification

Most of the libraries at the University of Illinois at Urbana-Champaign use the Dewey call number system; you are probably familiar with these call numbers from their widespread use in public libraries. A few University of Illinois libraries, however - e.g., Asian, Law, and Music - use another system for organizing materials called the Library of Congress (LC) system.

The LC system originated in the Library of Congress, a private library for senators and representatives in Washington, to organize materials on shelves. In recent decades, as LC has made its records available electronically, more libraries have adopted LC for both shelving and cataloging. Once an item is LC catalogued, you will need to understand the number to retrieve the physical item you have selected.

What Do the Parts of the Call Number Mean and How are Call Numbers Arranged on the Shelves?

  • Like Dewey, LC generally organizes materials by subject.
  • The LC number appears in three main parts, and may contain additional parts that together provide a unique identifier for the item.
  • One or more parts may be omitted; this represents the judgment of the cataloguer that the remaining parts suffice to provide a unique identifier.
  • The three main parts are organized in this way:
  1. a letter or letters (KF 801 .C65)
    A single letter represents a broad, general subject
    For Example: K = Law;
    multiple letters mean a narrower subject within it
    For Example: KF = US federal law.
    This part of the call number is arranged alphabetically on the shelves, so J would come before K which would come before KF
  2. a number (KF 801 .C65)
    This middle part further defines the subject.
    For Example: In the subject area of law, it designates a type of material. 801 = general/comprehensive works.
    To determine the arrangement of the call number on the shelves, read these numbers the way you would count: 30 comes before 300 which
    comes before 3000.
  3. one or more Cutter numbers (KF 801 .C65)
    Named after a cataloguer, this number represents the beginning letter of a person's (author, editor, etc.) last name with a number that interpolates it between other names beginning with the same letter
    For Example:
    Calamari, John D. = .C26
    Corbin, Arthur L. = .C65

    The above number may be preceded by a cutter number that further divides the subject, or gives some information about the form of the item, such as whether it is an outline, form book, or case book.
    To determine the arrangement on the shelves, read Cutter numbers the way you would read a decimal: .3 comes before .301 which comes before .31.
  • The LC number may have additional parts:
  1. a date: (KF 801 .C65 1960) which distinguishes among different editions of the same work;
  2. a volume number (KF 801 .C65 v.3A1960).

LC Classification Scheme

The Library of Congress Classification Scheme allows for greater precision in most fields and more room for expansion than the Dewey Decimal Classification System.

Each Library of Congress classification is represented by a set of capital letters and numbers. The first letter in the set indicates one of 21 major areas of knowledge.

A -- General Works
B -- Philosophy, psychology, and religion
C -- History: Auxiliary Sciences
D -- History: General and Old World
E -- History: America and U.S., general
F -- History: America and U.S., local
G -- Geography, anthropology, folklore, etc.
H -- Social sciences, economics, business, sociology
J -- Political Sciences
K -- Law
L -- Education
M -- Music
N -- Fine arts
P -- Philology, linguistics, language, and literature
Q -- Science
R -- Medicine
S -- Agriculture
T -- Technology
U -- Military Science
V -- Naval science
Z -- Bibliography and library science
I, O, X, and Y are not used

Additional information about the Library of Congress appears on its Web FAQ page at: http://lcweb.loc.gov/faq/