Understanding Call Numbers
Each book in the library has a unique call number. A call number is like an address: it tells us where the book is located in the library. Call numbers appear on the spines of books and journals and in the library's catalog. Note that the same call number can be written from top-to-bottom or left-to-right.
Understanding the numbers
Besides the materials in the Government and Geographic Information Collection, the call numbers used by the library are classified by subject, so you can often find several helpful books on the same shelf, or nearby.
The first sections of the call number represent the subject of the book. The letter-and-decimal section of the call number typically represents the author's last name. The last section of a call number is often the date of publication.
Types of call numbers
The library uses three different types of classification schemes to organize various collections and libraries.
- Library of Congress is used in our Music and Transportation libraries. As of January 2015, all new acquisitions receive Library of Congress call numbers.
- Dewey Decimal was used to classify the majority of the Libraries' collection until 2015.
- SuDoc (Superintendent of Documents Classification) call numbers are issued by the United States Government Printing Office for items published by the U. S. Government. The SuDoc Classification System is not a subject based system, instead items are arranged by the department or the agency issuing the publication, such as the FBI or the Department of Health. As a Depository for Government Documents, Northwestern University Library uses the SuDoc Classification System for all government documents.
For more information on understanding call numbers, as well as how to shelve and work with call numbers, visit the Call Numbers LibGuide.