Our understanding of the premodern past has been shaped by the questions and framing embraced by nineteenth- and early-twentieth-century historians. These early historiographic works both shaped and were shaped by modern national ideas and modern ideas about geography. These nineteenth and early twentieth-century national historians searched for authentic national cultures. Christian scholars across Europe looked to folk culture to find cultural authenticity and to political history to define national boundaries. Jewish historians, in turn, cast Jewish culture in the dichotomy of insularity and assimilation, similarly marking certain Jewish practices as ‘authentic’ and some as corrupted by ‘foreign’ influences. Both groups thus created perceptions of sharp cultural and religious boundaries that historically were much more permeable. This talk will explore how modern historians’ search for ‘authentic culture’ distorted historical reality of the medieval and early modern period in which religious practices, spaces, and cultural values of medieval and early modern Christians and Jews were more connected and social and cultural boundaries between the two communities more permeable, even if the two communities retained separate and distinct identities.