This document contains the principal papers from a 1981 symposium held to celebrate the completion of the 754-volume National Union Catalog, Pre-1956 Imprints. Papers by both those who use the National Union Catalog (NUC) and those who developed it are included. A brief preface describes the mission of the Center for the Book and the purpose of the conference. The introduction defines the NUC, chronicles its history, and discusses the impact of technology on all forms of bibliographical control, with particular emphasis on the NUC. The papers tell the story of how the NUC, a 14-year publishing project, came to be and how it is being used now. Papers include: (1) "The Library of Congress and The National Union Catalog" (William J. Welsh); (2) "The National Union Catalog and Research Libraries" (Gordon R. Williams); (3) "Editing the NUC" (David A. Smith); (4) "Publishing the NUC" (John Commander); (5) "Antiquarian Booksellers and The National Union Catalog: A Survey" (Bernard Rosenthal); (6) "Scholarly Uses of The National Union Catalog: An International Perspective" (Nicolas Barker); and (7) "Scholarly Uses of the National Union Catalog: A Bibliographic Saga" (William B. Todd). (THC)