This article traces the history of cataloging cartographic materials at the Library of Congress from its inception to the present day. The development and revision of general cataloging tools now used by catalogers, including MARC and AACR, are documented, as well as those tools used by the cartographic materials cataloging community, Library of Congress Classification, Class G; Map Cataloging Manual; and Cartographic Materials: A Manual of Interpretation of AACR2. The current effort to generalize the cataloging rules, to create an international cataloging code, Resource Description and Access, is also described.