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How do I?: Call Numbers

What you need to succeed in the library...

What are call numbers and how do I read them?

About Library of Congress Call Numbers 

Materials owned by academic libraries are organized by the Library of Congress System. Library of Congress call numbers connect the topic of the item with a location number associated with the topic. For example, materials on bicycles will appear in the TL 400 section of the collection.  TL is the letter combination assigned to transportation and vehicles.  

Each item in the library has its own call number that acts as the address of the item in the library.

Through the HELM catalog, patrons can get call numbers to use to locate materials in our collection.  In the HELM catalog, you will see the text of call numbers written from Left to Right. On the spines of books and on AV items, they appear in a series of top to bottom lines.

Call numbers on book spines and in the catalog

Why use call numbers? Use them so you can find a specific item OR use them to assist you in browsing an area of the collection that holds materials on your topic. Academic libraries tend to use the same call numbers and so you can browse another library's collection by using the call number you located here.

A call number gives your the exact location of the item, as if it were an address.  It's wise to know what section of the library holds the item you want. Call numbers start with as few as one and as many as three letters.

Click HERE for the Library of Congress Call Number classification.

The second (or sometimes there's even a third) letter in a call number narrows down the subject even more.  The next line of any LC Call number will be composed of numbers. Call numbers may contain multiple lines.  

In any call number, read the first line, find the letter or letters. Next, find the second line, since items on the same topic may share the same first two lines. You can find the more specific item by going to the next line, then the next line, and, finally a date. Usually items with the same call numbers and different dates reflect different editions of the same item.

This book is about bicycle repair:     

This book is about motorcycles:


You can see that their call numbers are very similar.  You need to look at the spine(s) of items carefully to tell them apart. In a few cases, the spines of items are so thin you will find the call number on the front left bottom corner of an item.