Library of Congress Classification System

last modified 2016-01-08T17:31:11-04:00

The Library of Congress classification system is a method of organizing books and other materials by subject. Materials are organized in an alpha-numeric system giving every item in the library a unique call number based on the primary subject of the book. This helps you both to locate specific items and to find similar books, movies, etc. by browsing the nearby items. 

How to Locate an Item on the Shelf

Although displayed as a single line in the catalog, the call number will be broken up into several lines on the spine of the book or DVD. Begin by looking at the first line, then the second line, etc, as follows:

call 2DS
The first line of a call number contains one or two letters. These letters should be read alphabetically; all call numbers beginning with B come before any beginning with C, and a call number beginning BC comes before BD.

The second line should be read in two pieces, separated by the decimal point. Read the first part as a whole number (e.g. five hundred and fifty-nine) and then read the numbers after the decimal point (e.g. point four six) from left to right. This means that .45 comes before .455, which comes before .5.

The third line is usually a combination of a letter and numbers, and may or may not begin with a decimal point (it is read the same either way). Begin with looking for the letter in alphabetical order, then read the remaining number as a decimal (e.g. H three eight, not H thirty-eight). If you have no letter, look for the item after call numbers that begin with Z on this line. If more letters or numbers follow, use the same rules.

The last line is the year the book was published (not always included for older works). These are shelved in chronological order, so 1985 comes before 1991 comes before 1992, etc.

Here is an example shelf of books with the call number order explained:

Image created with "Spines of the Penguin Poetry series" by Alan Trotter. This image available under a CC BY 4.0 license.

Not every call number will contain all of these pieces of information - if any are missing, the general rule of thumb is "nothing comes before something." Thus the call number LB 1050 would come before LB 1050 W54x 2004 in our example shelf.

If you have difficulty locating an item please check with a librarian or library staff member for assistance.

Understanding LCC System Call Numbers

These are the broad subject areas for the LCC system:

  • A - General Works (includes encyclopedias, almanacs, indexes)
  • B - Philosophy, Psychology, Religion
  • C - Auxiliary Sciences of History (includes archaeology, geneaology, biography)
  • D - History (includes general histories and the history of countries in the eastern hemisphere)
  • E-F - History of the Americas (includes North, South, and Central America)
  • G - Geography, Anthropology, Folklore
  • H - Social Sciences
  • J - Political Science
  • K - Law
  • L - Education
  • M - Music
  • N - Fine Arts (includes architecture, sculpture, painting, drawing)
  • P - Language and Literature
  • Q - Science (includes physical, biological, and computer sciences, as well as mathematics)
  • R - Medicine (includes health and human sexuality)
  • S - Agriculture
  • T - Technology (includes engineering, auto mechanics, photography, home economics)
  • U - Military Science
  • V - Naval Science
  • Z - Bibliography and Library Science
Each of the above are further subdivided into increasingly narrow topics, using additional letters and numbers. For example let's take this book:

Reporting Vietnam : Media and Military at War by William H. Hammond, call number DS559.46 .H38 1998

call no

  • DS represents the General Subject Area - in this case, History; Asia
  • 559.46 represent a more specific subject area - in this case the Vietnam War and press coverage
  • H38 stands for the author, Hammond, William. If there is no author, this line represents the title of the work
  • 1998 is the year that the book was published