A Library of Congress Control Number, or LCCN, is an identification number on the copyright page that contains the year a book was published and its unique serial number. The Library of Congress assigns the numbers to books before they are published if the people responsible for appointing the numbers believe a title might be added to the library’s shelves in the future. Even if a book receives an LCCN, it may not be added to the library’s collection. After all, there are over eight hundred miles of shelves in the Library of Congress, but there are still volumes that don’t make the cut.

Library of Congress Control Numbers allow librarians to find the proper cataloging information for titles that are published in the United States of America. They should not be mistaken for International Standard Book Numbers (IBSN), which makes each format of a book easily identifiable to librarians and booksellers. In the United States, if the author wishes to sell a title, the published work must have an IBSN, but it is not required to have a LCCN.

There are two types of Library of Congress Control Numbers. One type is called a Cataloging in Publishing, or CIP. It’s mostly used for books that are acquired by large publishing houses. Self-published authors and small presses may apply for a Pre-Assigned Control Number, or PCN. A title will be considered for a CIP or a PCN if it is over fifty pages in length, and it will be published in the United States.

The application process may be completed online, and it requires only basic information about the book, like the description and IBSN. It may take up to two weeks before the number is assigned to the submitted book. An author or publisher may refer to the site to check on the status of their work.

As a reader, it may not mean a lot to you if the book you select can be found at the Library of Congress. As an author, it may make you feel as though you’ve reached a milestone in your career if your book is shelved in the library established by Thomas Jefferson. Books published by the major publishing houses usually find a spot on the shelves of the Library of Congress, but books with Pre-Assigned Control Numbers may never be available at the nation’s largest library.

Getting approval to use the PCN is only part of the process. Once a book is published, the publisher or self-published author must send a copy of the book to the Library of Congress. Once there, it may take six months to a year before an author knows if the title has been accepted or rejected. The Library of Congress does not notify authors about the addition or rejection of their work. The author or a publishing company’s representative must check the catalog to see if the book appears on the list.

If you’re interested in applying for a Library of Congress Control number, you may visit https://loc.gov/publish/prepubbooklink. If you’d like to see the millions of titles available at the Library of Congress, go to https://catalog.loc.gov/vwebv/searchKeyword.