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SuDoc Call Numbers

SuDoc numbers are assigned by the Government Printing Office to materials published by federal agencies and distributed to Federal Depository Libraries in both paper and microfiche formats.  Northwestern University Libraries have been a depository library for more than 100 years and receives approximately 75% of the materials made available to depository libraries.


SuDoc numbers organize materials by the publishing agency, not by subject as in Dewey or LC.  Usually, but not always, the name of the agency provides the first letter(s) of the SuDoc call number.  

A few examples:

  • A - Agriculture
  • C - Commerce
  • D - Defense
  • E - Energy
  • ED - Education
  • EP - Environmental Protection Agency
  • J - Justice
  • L - Labor
  • S - State
  • Y - Congress

See a complete, current list.

Reading the number

ex:   T22.19:M54/990
T22.19 The STEM: All letters/numbers/punctuation before the colon. SuDoc classes are arranged alphabetically based on the leading letter(s) in the stem.  SuDoc classes file alphabetically no matter how many letters are used (ex. L comes before LC;  N comes before NAS which comes before NS). The number in the stem between the period and colon is a whole number (ex. HS 1.2: comes before HS 1.15:).
M54/990 The SUFFIXeverything that FOLLOWS the colon.