Library of Congress Control Number (LCCN)

Characteristics

An LCCN is composed of two main parts: a year identifier and a sequential number. The number is issued when the Library of Congress creates a catalog record; it is therefore tied to the bibliographic entry rather than the physical item itself. The LCCN does not encode subject, format, language, or location information and is not related to the Library of Congress Classification system.

• Assigned by the Library of Congress during cataloging.
• Serves as an identifier for a bibliographic record, not a classification code.
• Appears in national bibliographic exchanges and in many cataloging formats, including MARC records.

History and development

The numbering practice began in the late 19th century when the Library produced printed and card catalogs and sold cataloging cards to other libraries. Originally called the Library of Congress Card Number, the system provided a way to identify sets of catalog cards and the corresponding bibliographic records. Over time the scheme evolved in format and presentation; for example, the representation of the year portion changed to a four‑digit year in 2001 to avoid ambiguity between centuries.

Formats and notation

In cataloging practice the LCCN may be displayed with or without punctuation and often with leading zeros added to the sequence portion to create a uniform length for machine processing. Library systems and metadata formats typically store the number in a dedicated field so it can be used to match records across services. The LCCN is commonly found in the MARC 010 field in bibliographic records and appears in Library of Congress discovery interfaces and bibliographic exports.

Uses and significance

The LCCN is an important tool for bibliographic control and resource discovery. Libraries worldwide use it for record matching, authority control, interlibrary loan reference, and linking local holdings to the national catalog. Publishers and authors may also cite an LCCN when referring readers to an authoritative catalog entry or in the context of prepublication cataloging programs.

• Record linking: matches local metadata to the Library of Congress entry.
• Cataloging: used in shared cataloging and metadata exchange.
• Reference: allows precise retrieval of a Library of Congress record online.

Distinctions and related identifiers

The LCCN is one of several widely used identifiers in the bibliographic ecosystem. It differs from the ISBN and ISSN, which identify specific editions or serials, and from OCLC numbers, which identify records in a separate cooperative catalog. When consulting or citing an LCCN, it is helpful to remember that it points to a Library of Congress catalog record; it does not indicate subject classification, copyright status, or physical location. For authoritative information about assignment and format, consult the Library of Congress documentation and cataloging manuals.