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Understanding Library of Congress (LC) Call Numbers

This guide explains the Library of Congress Call Number system and how you can use it to find physical materials in the library

Understanding Library of Congress Call Numbers


One of the most confusing steps in the research process is locating library materials on the shelf. At Chalmer Davee Library, we use the Library of Congress Classification System to assign call numbers to most of the materials found in the library. Two exceptions are Federal Government Documents (Su.Docs.) and the Wisconsin Documents (WI Docs.) collections. If you need assistance in locating government documents, please ask at the Circulation Desk. 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, DVDs, CDs, etc.) 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, 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 - 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. The library has several locations:

  • AV Room
  • Curriculum Materials Collection (Upper Level)
  • Main Stacks (Upper Level)
  • New Book Shelf
  • Oversized (Upper Level)
  • Reserves
  • Popular Literature
  • Popular Reading

2) Check the Status of the book. The status will tell you if the book is Checked out, or if the book is Available.

3) If the book was recently published, it may be on the New Book Shelf located near the Circulation Desk.

For help please call (715-425-3321) or ask for help at the Circulation Desk.