Library of Congress Classification

The Library of Congress Classification is the classification system used by the Library of Congress and adopted by most large academic and research libraries in North America and internationally. Together with the Dewey Decimal Classification, it accounts for virtually all classification systems in use in US libraries, with approximately 95% of public libraries using DDC and most of the remainder using LCC.

Background

The central core of the modern Library of Congress was formed from books sold to the government by Thomas Jefferson after the British burned the original collection in the War of 1812. Jefferson's own classification system served the library through the nineteenth century, but by its end the collection had grown to over a million volumes and the system was inadequate.

In 1897, the seventh Librarian of Congress, John Russell Young, hired James Hanson (chief of the Catalog Department) and Charles Martel, who began developing a replacement. They evaluated several existing systems -- the Dewey Decimal Classification, Charles Ammi Cutter's Expansive Classification, the Index Medicus, and the Putnam Classification System from the Minneapolis Public Library -- before deciding to develop their own, drawing most heavily on Cutter's approach (Cutter died before completing his system). Young's successor, Herbert Putnam, continued implementation through his long tenure (to 1939), by which time all classes except K (Law) were well developed. The first outline was published in 1904.

Development of class K began with the first K schedule in 1969 and was not completed until the 2004 publication of subclass KB. Since 1996, the schedules have been available online, and since 2013, no new print editions have been issued. All updates are now distributed through the Cataloging Distribution Service entirely online.

Purpose and Scope

LCC was designed specifically for the Library of Congress's collections rather than as a universal classification of knowledge. It is essentially enumerative, listing all classes in officially published schedules that describe what books a library might actually hold. This practical orientation distinguishes it from the Dewey Decimal Classification, which attempts to classify all topics comprehensively. While less expressive than DDC in representing hierarchical relationships, LCC is extremely hospitable to new subjects, partly because five class letters remain unassigned.

Design and Organization

LCC divides knowledge into 21 main classes, each designated by a single letter:

Five letters (I, O, W, X, Y) are intentionally unassigned, providing significant room for future expansion. Most classes are further divided into two- and three-letter subclasses, with numerical ranges assigned to specific topics proceeding from general to specific.

Call Number Structure

A typical LCC call number includes: the class/subclass letters, a numerical topic range, one or more Cutter numbers (letter-number codes modeled after Cutter's Expansive Classification that further distinguish items, often encoding the author's surname), and the publication year. LCC call numbers tend to be shorter than those in DDC.

LCC should not be confused with Library of Congress Control Numbers (LCCN), which identify catalog records for books and authors, or Library of Congress Subject Headings (LCSH), which describe content using controlled vocabulary terms like "Glaciers" and "Glaciers -- Fiction."

Variations and Extensions

The National Library of Medicine classification system (NLM) uses the letters W and QS-QZ, which LCC has left available. Some libraries use NLM alongside LCC for medical materials, eschewing LCC's R, QM, and QP schedules. Canadian universities and the Canadian National Library use the subclass FC for Canadian history, which LCC has informally reserved but not officially adopted.

Governance and Maintenance

The various schedules are maintained and revised by the Library of Congress's Policy and Standards Division in conjunction with subject experts. Updates are distributed through the Cataloging Distribution Service and the Classification Web subscription product. The system is continuously updated online.

Criticisms

LCC has been criticized for lacking a sound theoretical basis, as many classification decisions were driven by practical needs rather than epistemological considerations. The earlier-developed schedules (D, E, F, B) reflect American, European, and Christian biases, while the later-developed K (Law) provides more balanced global coverage. Updating biased schedules is generally considered impractical due to the massive workload involved and the entrenchment of discipline-based classes in library users' expectations. Like all classification systems, LCC struggles with interdisciplinary topics and has been noted for difficulties in locating works related to or authored by marginalized groups. Some libraries with specialized minority collections have adopted alternative systems such as the Harvard-Yenching Classification for Chinese language materials.

Related Standards

• Library of Congress Subject Headings (LCSH) -- the companion controlled vocabulary for subject access
• Library of Congress Name Authority File (LCNAF) -- the authority file for names used in cataloging
• Dewey Decimal Classification (DDC) -- the other major US library classification, used primarily by public and smaller academic libraries

Further Reading

• LCC Classification Outline
• Classification and Shelflisting
• Classification Web (subscription)