This article is an approach to the production processes of the first two volumes of the Monumental Catalog of Spain written by Manuel Gómez Moreno. Through the study of the historian's personal correspondence, the social network that was interwoven during his travels for the elaboration of the volumes was created and analyzed. This analysis provides insight into the social network that helped and supported the work of researching, cataloging and inventorying Spanish cultural heritage. This study consolidates the research on the different sectors of society that contributed to the collection of data and information that would later be reflected in the first two volumes of the Monumental Catalogue.