Superintendent of Documents Classification is a system of library classification developed in the office of the Superintendent of Documents of the United States Government Publishing Office (GPO) at the turn of the 20th century. The call numbers are based upon issuing agency / department. For example, A call numbers are publications of the Department of Agriculture, C is Commerce, D is Defense, and so on.
While most academic libraries use the Library of Congress (LC) classification system to organize materials by subject/discipline, many still catalog government documents with SUDOC. At Auraria Library, government issued maps and DVDs are catalogued using the SUDOC classification system, while all other government documents use the LC classification system.