With the aim of improving our knowledge about the role of markets in the process of genesis and consolidation of feudalism, this paper analyses the origin of the network of exchanges that was developed in the Penedès region between the 9th and the 12th century. The integrated study of documentary, archaeological, and territorial sources, and the use of Geographic Information Systems (GIS) in the representation and analysis of data, allow us to approach the process of interaction of the network of medieval markets. The oldest commercial gathering of the Penedès region was the one held in La Granada, located along the axis of the Via Augusta. From the 12th century onwards, the importance of this market was overshadowed by the emergence of the market and fair of Vilafranca, which soon became the most important market in the area. The study of the political and economic motivations that caused this change in the hierarchy helps us understand the territorial and commercial logic of feudalism. We are looking at a strong and well articulated market network, led by Vilafranca del Penedès and reinforced, from the thirteenth century on, by the foundation of new markets and fairs able to supply, with their radius of influence, the entire territory of Penedès.