Classification: Systems of Organization, or How Libraries Do It (Part I: The United States)

Let's look at some of the systems that libraries use to organize their collections.

First, let's define classification. Greer, Grover, and Fowler (2007) define classification as "a system for organizing knowledge" (p. 112). Many classification systems exist in the world, some are used very broadly, others are specific to a particular library, especially a library with a small, highly specialized collection.

Libraries in the United States generally use one of two systems to organize the materials in their collections: the Dewey Decimal Classification System or the Library of Congress Classification System. These systems are also used around the world.

The Dewey Decimal Classification (DDC) System:
Melvil Dewey was born in 1851 in upstate New York. Dewey was greatly influential in the field of librarianship, founding the American Library Association, the Library Journal, and the first library school at Columbia University. He is most famous, however, for the classification system that he created in 1876 while working at Amherst College. His work at the college library sparked an interest in the organization of library materials and he published his ideas in A Classification and Subject Index for Cataloging and Arranging the Books and Pamphlets of a Library, which became known as the Dewey Decimal Classification (DDC) system (Byers, 1998).

Dewey's system classifies information by subject, with 10 primary categories, the "hundreds" (e.g. in the 100s section you will find materials on philosophy and psychology; in the 200s, Religion; the 700s, Art, etc.). Each category is then subdivided by tens and ones and then decimals (you knew there were going to be decimals in all of this, didn't you ?) creating numbers that lead to more and more precise subject listings.
In the United States, the DDC is primarily used in school and public libraries.

The Library of Congress (LoC) Classification System
The Library of Congress classification system was developed at the turn of the 20th century to classify the holdings of the Library. The Library's original classification scheme was created by Thomas Jefferson. Between 1815 and 1890 the collection grew from around 7,000 books to almost 1 million. By this point, the collection had outgrown the scope of Jefferson's system, and the decision was made to develop a new system (Chan, 2007).

While the DDC uses numbers to classify information, the LoC system uses a combination of letters and numbers. There are 21 broad categories, like Dewey's hundreds divisions, each beginning with a different letter of the alphabet. (The letters i, o, w, x, and y are not used).
The Library of Congress Classification System is used primarily in research and academic libraries (and at the Library of Congress, of course!) ("Library of Congress," 2008).