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).
Wikipedia organized by the Library of Congress Classification
|B||PHILOSOPHY. PSYCHOLOGY. RELIGION|
|C||AUXILIARY SCIENCES OF HISTORY|
|D||HISTORY: GENERAL AND OLD WORLD|
|G||GEOGRAPHY. ANTHROPOLOGY. RECREATION|
|M||MUSIC AND BOOKS ON MUSIC|
|P||LANGUAGE AND LITERATURE|
|Z||BIBLIOGRAPHY. LIBRARY SCIENCE. INFORMATION RESOURCES (GENERAL)|
Letter classes I, O, W, X and Y are not standardly used.
See also: Wikipedia organised according to Roget's Thesaurus outline