Lesson 1: The Dewey Decimal Classification System


Most public and school libraries in many parts of the world use the Dewey system, so called after its creator, Melville Louis Kossuth Dewey (1851-1931). Dewey created the system in 1876 as a method of logically organizing small libraries’ collections. The organizational scheme is based on a limited number of general categories and short call-numbers. The system is based on ten classes of subject (000-999), which are then further subdivided. These are referred to as call numbers, and every book in the library is given a unique call number to serve as an address for locating the book on the shelf in the most appropriate area of the library.

Every book in a library or archive is given a unique call number to serve as an address for locating the book on the shelf. In the case of the Dewey number, a call number consists of one of the ten classification codes or a more finite code representing a specific division of the main class. Most experienced genealogical researchers will certainly recognize 929 as the division that includes genealogy, names, and insignia. In addition, there is a further subdivision, which follows the division to differentiate, between the type of information or content. The number 929.073 is the Dewey Decimal number for the book, Who’s Who in America. The family history titled Ten Thousand Plunketts, by Emma Plunkett Ivy, is further differentiated with what is called a “cutter number,” based on Dewey’s system and further refined by Charles A. Cutter (1837-1903). The cutter number would ordinarily by 929.1 IVY and, since it is in two volumes, the volumes are listed as 929.1 IVY V.1 and 929.1 IVY V.2 respectively. The classification numbers in this system are assigned by catalogers in the library who obtain or download them from an organization called the Online Computer Library Center (OCLC). The cataloger may abridge the number somewhat to adhere to the individual library’s classification and organization scheme but the numbers used are usually pretty close to what I’ve described above. Once the classification number is assigned, a spine tag is produced and applied to the book, it’s determined whether it is a circulating or non-circulating item, and is then shelved or filed for access.

Inasmuch as genealogists use many different types of books, it is essential to recognize that simple author or title searches if insufficient to yield all the materials which might be pertinent and useful to our research. Simply making a beeline to the 929s in a public library is very unlikely to yield all the information you may want or need. While 929 is a great place to start, the catalog will also direct you to other areas in the library’s collection. For example, you may find Kentucky cemetery records in 929.3, but you will also a bicentennial history of Kentucky in 976.9 and an atlas of that state in 912.9. And while a book about Polish roots might be filed under 929.1094, a Polish-English/English/Polish translation dictionary to help you understand original documents would be found in 491.8532. As you can see, genealogical reference sources are locating in many Dewey classifications throughout the library, and the library’s catalog is your key connection point to these diverse research reference resources.