How To Interpret a SuDoc Number

The SuDoc classification system is designed specifically for United States government documents. A SuDoc number is assigned by the office of the Superintendent of Documents (SuDoc) of the Government Printing Office. Unlike most classification systems, SuDoc numbers are not based on subject. Instead they are based on the agency which issued the publication and because government agencies are organic -- they grow, split, merge, die, etc. -- SuDoc numbers can be quite simple or very complex. For instance,

SuDoc NumberItem
I 1.1:917Reports of the Department of the Interior. 1918.
I 29.6/6:F 75/988Ford's Theatre and the House Where Lincoln Died. 1988.
I 53.11/4:43109-E1-TM-100/991Ramshorn, Wyoming Surface Management Map. 1991.

To read a SuDoc number, you must begin by recognizing the constituent parts. First off, SuDoc numbers are divided, usually at the colon, into two parts -- the stem and the book number which then combine to make a complete SuDoc number. We'll use I 29.6/6:F 75/988 as an example.

image of [ I 29.6/6:F 75/988 ] SuDoc number


All SuDoc numbers begin with one to four letters. Each department or independent agency of the United States government is assigned a letter or combination of letters of the alphabet based on the name of the agency. For instance, the Commerce Department has been assigned the C. The Defense Department uses the D, the Justice Department the J, etc. X and Y are reserved for Congress. Newer agencies tend to be assigned multi-letter designations -- the Social Security Administration, for instance, has been assigned SSA. See more examples.

Therefore, in our example, the I indicates that the Department of the Interior issued the publication.

Subordinate bureaus within each agency are assigned numbers beginning with 2. The number 1 is reserved for the parent organization. (There is always a space between letters and numbers in the SuDoc system, unless there is punctuation between them.) The bureau number is then divided from the rest of the SuDoc number by a period. (Punctuation in a SuDoc number always acts as a divider, not as a decimal point.)

Thus, I 29. stands for the National Park Service, the 28th bureau of the Department of the Interior.

Following the period, each series issued by that bureau is also assigned a number. New series which are closely related to an existing series are "attached" to the existing series by putting a slash after the existing series number and then adding another letter or number. For instance:

SuDoc NumberItem
I 29.6:National Parks Information Circulars
I 29.6/2:National Seashores, Information Circulars
I 29.6/3:National Lakeshores, Information Circulars
I 29.6/4:National Rivers, Information Circulars
I 29.6/5:National Scenic Trails, Information Circulars

Sometimes the number after the period can be rather complicated, involving both slashes and dashes to relate series to each other. The stem then usually ends with a colon.

In our example, I 29.6/6: stands for the National Historic Site Information Circulars series from the National Park Service of the Department of the Interior.

A list of all the current series available from the United States Government Printing Office can be found in the List of Classes of United States Government Publications Available For Selection by Depository Libraries (click on link to "Latest Print Version"). An historical list of all the series that have been created by the Government Printing Office can be found in Andriot's Guide to U.S. Government Publications (Z 1223 .Z7 A572 2012 -- Documents/Reference).

Book Number

After the stem, each individual issue or publication in a series is assigned a unique identifier, called a book number, following the colon. Unnumbered monographs, numbered monographic series, and serials, all have different types of identifiers.


For unnumbered monographs, the identifier is usually an alphanumeric Cutter number that, in SuDocs, is based on a word in the item's title (such as R 11 for Racketeer).

For numbered series, the identifier usually is:


For serials (magazines, journals, annual reports, etc.), the identifier is usually:

Putting It All Together

Returning to our original example:

[ I 29.6/6:F 75/988 ]

Therefore I 29.6/6:F 75/988 stands for the 1988 edition of Ford's Theatre and the House Where Lincoln Died in the series National Historic Site Information Circulars from the National Park Service of the Department of the Interior of the United States of America.

More information

For more information on SuDoc classification, check out An Explanation of the Superintendent of Documents Classification System.