This essay examines sources related to the creation and promulgation of the first codification of Aragonese territorial law in the mid-thirteenth century. The Fueros de Aragón have proven to be one of Europe's most durable bodies of laws, having persisted in some form or another for more than a millennium. In exploring the process by which Aragonese law was first codified, this essay expands our understanding of the evolution of medieval law. At the same time, it offers an occasion for questioning the origins of a written legal tradition that has defined historical and contemporary conceptions of Aragonese political identity within Spain. Of particular interest here is the tension that exists between longstanding assumptions about the origins of the first code of Aragonese law and the medieval sources that have something to say about it. In order to discern the process by which the fueros were codified, this essay scrutinizes the narrative prologues to multiple Latin and romance texts of the Fueros de Aragón as they are found in medieval manuscripts and early printed texts. The essay also considers the implications that these findings have for ongoing scholarship on the institutionalization of the Fueros de Aragón in Aragonese history.