Throughout the 16th century the Basques were creating a network of power from which they could participate in or control the economic activities that the route to the Indies generated in the cities of Seville and Cadiz. The protectionist policy of the Crown, the marine tradition of the Basque people and the centuries of experience of traders were some of the factors that facilitated this situation. This research analyzes the destination and distribution of Basque manufacturing exports, as well as the structure and activity of the commercial companies established in Seville and the funds sent back to the Basque Country. The publication highlights the historic opportunity lost in the Modern Age to maintain the links between the Basque iron and steel industry and its traditional iron foundries.