National Union Catalog

The National Union Catalog is divided into two series: the Pre-1956 Imprints is a 754-volume set containing all older records in a consolidated alphabetical format, while post-1955 volumes continue to be published serially.

[6] The complete title of this work describes its purpose and scope:[7] The NUC of Pre-1956 Imprints is published in 754 volumes, containing over 528,000 pages.

In an effort to simplify research, it was decided in the 1960s to collect and publish all of the references to pre-1956 imprints in a single alphabetical listing.

Over the next 14 years, about five 600-page volumes were published each month until the NUC of Pre-1956 Imprints was completed, largely superseding the older Library of Congress Catalog of Printed Books.

It represented a monolithic achievement in the ongoing quest by libraries to streamline access to the world’s literature."