Library of Congress Classification
The Library of Congress Classification (LCC) is a system of library classification developed by the Library of Congress in the United States. It is used by most research and academic libraries in the U.S. and several other countries.

LCC should not be confused with LCCN, the system of Library of Congress Control Numbers assigned to all books (and authors), which also defines URLs of their online catalog entries, such as "42037605" and "https://lccn.loc.gov/42037605". The Classification is also distinct from Library of Congress Subject Headings, the system of labels such as "Boarding schools" and "Boarding schools—Fiction" that describe contents systematically. Finally, the classifications may be distinguished from the call numbers assigned to particular copies of books in the collection, such as "PZ7.J684 Wj 1982 FT MEADE Copy 1" where the classification is "PZ7.J684 Wj 1982".

The classification was invented by Herbert Putnam in 1897, just before he assumed the librarianship of Congress. With advice from Charles Ammi Cutter, it was influenced by his Cutter Expansive Classification, the Dewey Decimal System, and the Putnam Classification System (developed while Putnam was head librarian at the Minneapolis Public Library). It was designed specifically for the purposes and collection of the Library of Congress to replace the fixed location system developed by Thomas Jefferson. By the time Putnam departed from his post in 1939, all the classes except K (Law) and parts of B (Philosophy and Religion) were well developed.

LCC has been criticized for lacking a sound theoretical basis; many of the classification decisions were driven by the practical needs of that library rather than epistemological considerations. Although it divides subjects into broad categories, it is essentially enumerative in nature. That is, it provides a guide to the books actually in one library's collections, not a classification of the world.

In 2007 "The Wall Street Journal" reported that in the countries it surveyed most public libraries and small academic libraries used the older Dewey Decimal Classification system.

The National Library of Medicine classification system (NLM) uses the initial letters "W" and "QS"–"QZ", which are not used by LCC. Some libraries use NLM in conjunction with LCC, eschewing LCC's "R" for Medicine. Others use LCC's "QP"–"QR" schedules and include Medicine "R".
Q48473
library classification
Concept
Q131454
Library of Congress
LOC
Q620946
Library of Congress Control Number
MEDIA
Q42253
URL
Concept
Q1823134
Library of Congress Subject Headings
ORG
Q924790
Herbert Putnam
PER
Q1064010
Charles Ammi Cutter
PER
Q5196943
Cutter Expansive Classification
LOC
Q48460
Dewey Decimal System
Concept
Q25052493
Putnam Classification System
MEDIA
Q689456
Minneapolis Public Library
PER
Q11812
Thomas Jefferson
PER
Q9471
epistemological
Concept
Q2704791
enumerative
UNK
Q164746
The Wall Street Journal
MEDIA
Q48460
Dewey Decimal Classification
Concept
Q986957
National Library of Medicine classification
LOC
Q621080
Library of Congress Classification
MEDIA
1982-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
1982
DATE
1982-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
1982
DATE
1897-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
1897
DATE
1939-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
1939
DATE
2007-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
2007
DATE
+42037605^^http://www.w3.org/2001/XMLSchema#decimal
42037605
NUMBER
+42037605^^http://www.w3.org/2001/XMLSchema#decimal
42037605
NUMBER
+7^^http://www.w3.org/2001/XMLSchema#decimal
7
NUMBER
+684^^http://www.w3.org/2001/XMLSchema#decimal
684
NUMBER
+1^^http://www.w3.org/2001/XMLSchema#decimal
1
NUMBER
+7^^http://www.w3.org/2001/XMLSchema#decimal
7
NUMBER
+684^^http://www.w3.org/2001/XMLSchema#decimal
684
NUMBER
instance of
maintained by
based on