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Call Numbers (Library of Congress Classification System): Home

Finding a Physical Book

When you look up a book in the Library's online catalog, the call number listed for a book is how you will find it on the shelf. Call numbers are usually located on the spine of the book facing out when the book is on the shelf. The call numbers are arranged alpha-numerically.


Catalog record for "Declutter your mind: how to stop worrying, relieve anxiety, and eliminate negative thinking." Text "McGraw-Page Library Circulating Books - Second Floor" is underlined, and call number BF637.S4 D365 2016 is highlighted. An arrow points from the call number to the picture of this book on the shelf among other books. The call number on the spine of the book is circled. A second arrow points from the circled call number to a zoomed in picture of the book and call number so the number can be easily seen on the book.

What is the Library of Congress Classification System?

College and university libraries use the Library of Congress (LC) Classification System to organize their books and other resources. It was originally developed by and for the Library of Congress in Washington, D.C., to help them organize their library collections. The benefit of having a standard classification system is that no matter what academic library you visit, your research topic should be located at the same call number.

How to Read Library of Congress Numbers

When you see a Library of Congress (LC) call number during your research, notice that it is written a bit differently than it will appear on the book spine. In the catalog, it reads straight across, but on the book spine, it is broken down into components to help it fit on the book better and make it easier to read.

  • Books are arranged alphabetically. The first group of letters and numbers describe the subject of the book. 
  • The Cutter number follows the period (.) and often indicates the author, editor, or title of the book.
  • The year of publication follows the Cutter number to indicate the edition.

Call number BF637.S4 D365 2016. BF637.S4 is bracketed and defined as Applied Psychology.  D365 is bracketed and defined as the author's names: Davenport. 2016 is bracketed and defined as publication date.

Call numbers on the shelf

Call numbers are arranged alpha-numerically on the shelves. This means:

  • A comes before B, BA comes before BD
  • The numbers following the letters are treated like a typical decimal number: 636 comes before 637, 637.35 comes before 637.7
  • The first letters after the decimal point are alphabetical and then the numbers are treated like decimals. So .R comes before .S and .S34 comes before .S4
  • The next set of numbers are treated alphabetically and like whole numbers: C365 comes before D365 and D365 comes before D544.
  • If books have exactly the same call number but the publication dates are different, the earlier publication year comes first.

Take a look at the image below to see how this might look on a shelf:

Five "dummy" book spines show the following call numbers in this order: BD638 .B335 2013, BF637.35 .S34 S65 2008, BF637.7 .S4 D365 2016, BF637.7 .S4 D544 2016, BF637.7 .S5 D544 2020. The following notes point to specific elements of the call numbers, indicated that BD comes before BF, 637.35 comes before 637.7, .S34 comes before .S4, D365 comes before D544, and 2016 comes before 2020.

Quick Links to Call Number Subjects

Click the links below to explore topics using guides created by the Library of Congress in Washington, D.C.

Find the topic you're interested in and go to the second floor of the Library to browse the book collection and see if we have any books on that topic. It's always a good idea to check the catalog, too, since we have over 500,000 e-books!


A - General Works

B - Philosophy, Psychology, Religion

C - Auxiliary Sciences of History

D - World History

E/F- History of the Americas

G - Geography, Anthropology, Recreation

H - Social Sciences

J - Political Science

K - Law

L - Education

M - Music and Books on Music

N - Fine Arts

P - Language and Literature

Q - Science

R - Medicine

S - Agriculture

T- Technology

U - Military Science

V - Naval Science

Z - Bibliography, Library Science, Information Resources (General)