Library of Congress Classification: Definition and Links by Encyclopedian.com

The Library of Congress Classification (LCC) is a system of library classification developed by the Library of Congress. It is used by most research and university libraries in the U.S. (and several other countries), although most public libraries continue to use the Dewey Decimal Classification (DDC).

The classification was originally developed by Herbert Putnam with the advice of Charles Ammi Cutter[?] in 1897 before he assumed the librarianship of Congress. It was influenced by Cutter Expansive Classification and DDC, designed for the use by the Library of Congress. The new system replaced a fixed location system developed by Thomas Jefferson. By the time of Putnam's departure from his post in 1939 all the classes except K (Law) and parts of B (Philosophy and Religion) were well developed. It has been criticized as lacking a sound theoretical basis; many of the classification decisions were driven by the particular practical needs of that library, rather than considerations of rationality. In particular, the classification often shows bias towards the United States and towards Christianity.

Although it divides subjects into broad categories, it is essentially enumerative in nature.

The National Library of Medicine uses unused letters W and late Qs. Some libraries use NLM in conjuction with LCC, not using LCC's R (Medicine).