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At FOUNDERS : Understanding the Library of Congress Classification Scheme: Library of Congress Call Numbers

Understanding Library of Congress Call Numbers


One of the most confusing steps in the research process is locating library materials on the shelf. At Founders Library, we use the Library of Congress Classification System to assign call numbers to most of the materials found in the library. The exception is the paper periodicals collection which file alphabetically by title.This guide will provide an introduction to understanding and using Library of Congress Call Numbers.

What is a call number?

Everything that is located in the library (books, videotapes, DVDs, CD, LP records) has a call number and every call number is unique. Basically, call numbers tell you where to find materials in the library. Call numbers group materials together that are on the same subject, so if you browse the shelves after you find the first book you are looking for, you will find other books on your topic or on a similar topic nearby. For example, a book on American agriculture/farming is located at S441 while books on world agriculture/farming are located at S439, right before the books on American agriculture.

How do I read a call number?

When you search the library's catalog to find materials in the library, you will see the call number displayed in a single line like this:

SF 281.M355 2004

But when you look on the shelf, you will see the call number displayed like this:







SF Read the first letter in alphabetical order; a single letter (s) comes before two letters (SF)
281 Read the second line as a whole number (1,3,6,9,12,55,135, etc)
.M355 This line is a combination of a letter and several numbers. Read the letter alphabetically first, and then read the number as a decimal.
2004 This is the year of publication. Note: some books will not have this.


Do I need the whole call number to find what I am looking for?

Yes, each item on the shelf will have its own call number and since many call numbers begin with the same letters, you will need the rest of the call number to find your specific book, video, DVD, etc. If you have the whole number, it will be easier and quicker to find what you are looking for.

I cannot find the item on the shelf - LOCATION, LOCATION, LOCATION! - now what do I do?

1) Check to make sure you are looking in the correct "Library Location." The library location tells you specifically what part of the library your item is located. Look for the Call Number Guide at the Kiosks and at the Circulation Desk.  The library has several locations:

  •  Stacks  - 1-10
  • New Book Shelf
  • Reserves
  • Reference Stacks
  • DVD's and CD's
  • Art Books

2) Check the Status of the book. The status will tell you if the book is checked out, or if the book is on the shelf.


How do you put call numbers in order?

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.) Editions are often arranged by date or by the date and letters.

For help please ASK THE LIBRARIAN or email:

Why did Founder library switch over to LC call numbers for books?

This change will:

  • Better prepare our high school students for library environments at academic institutions
  • Bring us in line with research library standards
  • Create a more welcoming research environment for incoming faculty and researchers already familiar with LC

How can I tell the difference between Dewey Decimal call numbers and Library of Congress call numbers?

Dewey numbers start with numbers while LC numbers start with one or two letters.  

What is the differnce between Dewey Decimal call numbers and the Library of Congress call numbers?

The Library of Congress Classification (LCC) system was developed at the turn of the 20th century and was specifically created to categorize books and other items held in the Library of Congress. It features 21 (I, O, W, X, and Y are not used)  subject categories with resources being identified by a combination of both letters and numbers. For example, books on education are identified with a call number that begins with the letter “L” and those on political science under “J.” The number of classes and numerous subclasses is not restricted. Specific topics and geographic areas are often represented by alphabetic Cutter lists.

The Dewey Decimal Classification (DDC) system was developed in 1876 as a means to organize all knowledge.  The DDC uses notation in Arabic numerals, well-defined categories, well-developed hierarchies, and a rich network of relationships among topics. The ten basic classes are organized by disciplines or fields of study.  Each main class is further divided into ten divisions, and each division into ten sections. Except for a few optional provisions, the DDC notation is strictly numeric.