In the Region of Aisén, in Chilean Patagonia, musicians claim Argentine popular music from the early twentieth century as regional tradition, and call on it to express local identifications and Chilean patriotism. This seemingly incongruous form of traditionalism is rooted in narratives of Aisén’s early history, when Chilean settlers depended on Argentina for their survival in marginal, frontier circumstances. This article introduces the concept of the "post-frontier" to explain the position from which residents of Aisén claim this music as their own. This research opens new territory in the study of transnational music, tracing the various ways in which temporality acts upon and within notions of regional identity, national belonging, and transnational affinity.