The Library of Congress Control Number or LCCN is a serially based system of numbering books in the Library of Congress in the United States. This numbering system has been in use since 1898. It has nothing to do with the contents of any book, and should not be confused with Library of Congress Classification. Library of Congress, Jefferson building The Library of Congress is one of four official national libraries of the United States (along with the National Library of Medicine, National Agricultural Library, and National Archives and Records Administration). ... Library of Congress reading room The Library of Congress Classification (LCC) is a system of library classification developed by the Library of Congress. ...

In its most elementary form the number includes a year and a serial number. The year has two digits for 1898 to 2000, and four digits beginning in 2001. The three ambiguous years are distinguished by the size of the serial number. There are also some peculiarities in numbers beginning with a "7" because of an unsuccessful experiment applied between 1969 and 1972.

Serial numbers are six digits long and should include leading zeros. The hyphen that is often seen separating the year and serial number is optional.

Librarians all over the world use this unique number in the process of cataloging most books which have been published in the United States. It helps them reach the correct cataloging data (known as a cataloging record), which the Library of Congress and third parties make available on the Web and through other media.

See http://www.loc.gov/marc/lccn_structure.html for more details.

See Also

• ISBN International Standard Book Number.