Library of Congress Control Number (LCCN)
The LCCN is a unique identification number that the Library of Congress assigns to titles prior to publication. The LCCN is not the same as a copyright registration with the Library of Congress. Librarians use the LCCN to access the associated bibliographic record in the Library of Congress’s database or to obtain information on various book titles in other databases. The publisher prints the LCCN on the copyright page in the following manner: Library of Congress Control Number: 2001012345.
Only US book publishers are eligible to obtain an LCCN. To receive an LCCN, publishers must list a US place of publication on the title page or copyright page and maintain an editorial office in the country capable of answering substantive bibliographic questions.
There is no charge for registering, but the publisher must send a copy of the “best edition” of the book for which the LCCN was pre-assigned immediately upon publication to the Library of Congress. The “best edition” essentially means the one that is made of better material. So, if you had a hardcover and a paperback version of your book, you’d submit the hardcover. Books published only in electronic form are ineligible for an LCCN. Unlike an ISBN, the LCCN is assigned to the work itself, not any specific format, and doesn’t change with each new edition.
Should you wish to apply for an LCCN on your own, the first step is to complete the Application to Participate and obtain an account number and password, which takes one to two weeks.