After the Christian conquest of Toledo in 1085, the region north of the Duero river lost its strategic significance and frontier status, quickly becoming the backwater of the Castilian Reconquest. Seeking to counterbalance the current fascination with Iberian frontier societies, this dissertation draws attention to the major role the towns along the Castilian portion of the Camino de Santiago (“The Milky Way”) played in the history of Jewish-Christian relations in Iberia. At the heart of this study lies the argument that the socio-political foundations for Jewish-Christian coexistence (convivencia) in the kingdom of Castile were forged in northern Castile-León during the early period of Jewish settlement along the Camino. The dissertation traces the evolution of these norms and institutions through the thirteenth century, when their viability was first tested, and into the fourteenth century, when serious fissures developed in the host society’s toleration for the Jewish minority. Most notably, the Jews’ special role as suppliers of revenue for the royal treasury put a strain on the Jewish communities’ resources and became a major source of tension between the Jews and their Christian neighbors. Ultimately the dissertation suggests that the Castilian model of Jewish-Christian coexistence was similar to northern European examples, and was not—as is often argued—uniquely Iberian.