In this sweeping account of life within the United States-Mexican border zone, acclaimed urbanist and geographer Michael Dear traces the border's long history of cultural interaction, from exchanges between the region's numerous Mesoamerican tribes onwards. Once Mexican and American settlers met at the Rio Grande and the southwest in the nineteenth century, new forms of interaction evolved. But as Dear warns in his bracing study, this vibrant zone of cultural and social amalgamation is in danger of fading away because of highly restrictive American policies and the violence along Mexico's side of the border. As he explains through analyses of the U.S. border security complex and the emerging Mexican narco-state, the very existence of the "third nation" occupied by both Americans and Mexicans is under serious threat. But through a series of evocative portraits of contemporary border communities, he shows that the potential for revitalizing this in-between nation still remains.