Understanding Library of Congress Call Numbers

The majority of books that you will come across in the Arts & Sciences Libraries will have a Library of Congress Call Number. Call number labels are located on the lower part of the spine of the book. Reference materials, in addition, will be marked UGL REF or SEL REF on the call number label.

You can think of a call number as a book's address on the shelf. The first line in a Library of Congress call number classifies the item by its subject according to the LC Classification System. The entire call number should be noted in order to locate the item.

• LC call numbers are first arranged alphabetically, according to the letter or letters at the beginning of the call number, which correspond to the subject matter of the item.
  Example: Call numbers beginning with P are followed by PA, PB, PC, etc.

• Within the alphabetical section, books are arranged by the number(s) that follow. Notice that these numbers are regarded as whole numbers. For instance, PS 1200 comes after PS 345.
  Example: QA 56 before QA 234 before QA 234.57 before QA 234.8

• The next lines are alphabetic, then numeric as a decimal. The numerical part of this section is a decimal number, not a whole number. Use alphabetical order first, then the decimal extension to put the call numbers in correct sequence. (A3113 would come before A4, because 0.3113 is smaller than 0.4.)
  Example: HV 1431 .B7 before HV 1431 .B83 before HV 1431 .F25 before HV 1431 .F7

• Editions are often arranged by date or by the date and letters.
  Example: PS 3525 .I52 1971 before PS 3525 .I52 1973 before PS 3525 .I52 1973a

Guide to Library of Congress Classification System

A General Works (Encyclopedias, Almanacs, Directories)

B Philosophy, Psychology, Religion

C History (Auxiliary Sciences-Archaeology, Genealogy)

D History (General and all except North and South America)

E History (General U.S.)

F History (Local U.S., Canada, Mexico, South America)

G Geography, Anthropology, Folklore, Dance, Sports

H Social Sciences

J Political Science

K Law

L Education

M Music

N Fine Arts

P Language and Literature

Q Science

   QA  Mathematics

           QA75.5 - QA76.95   Computer Science

   QB  Astronomy

   QC  Physics

   QD  Chemistry

   QE  Geology

   QH  Natural history - Biology

   QK  Botany

   QL  Zoology

   QM  Human anatomy

   QP  Physiology

   QR  Microbiology

R Medicine

S Agriculture

T Technology

   TA  Engineering (General). Civil engineering

   TC  Hydraulic engineering. Ocean engineering

   TD  Environmental technology. Sanitary engineering

   TE  Highway engineering. Roads and pavements

   TF  Railroad engineering and operation

   TG  Bridge engineering

   TH  Building construction

   TJ  Mechanical engineering and machinery

   TK  Electrical engineering. Electronics. Nuclear engineering

   TL  Motor vehicles. Aeronautics. Astronautics

   TN  Mining engineering. Metallurgy

   TP  Chemical technology

   TR  Photography

   TS  Manufactures

   TT  Handicrafts. Arts and crafts

   TX  Home economics

U Military Science

V Naval Science

Z Bibliography, Library Science, Publishing Industry