Extraordinary change is under way in the Alto Urubamba Valley, a vital and turbulent corner of the Andean-Amazonian borderland of southern Peru. Here, tens of thousands of Quechua-speaking farmers from the rural Andes have migrated to the territory of the Indigenous Amazonian Matsigenka people in search of land for coffee cultivation. This migration has created a new multilingual, multiethnic agrarian society. The rich-tasting Peruvian coffee in your cup is the distillate of an intensely dynamic Amazonian frontier, where native Matsigenkas, state agents, and migrants from the rural highlands are carving the forest into farms. Language, Coffee, and Migration on an Andean-Amazonian Frontier shows how people of different backgrounds married together and blended the Quechua, Matsigenka, and Spanish languages in their day-to-day lives. This frontier relationship took place against a backdrop of deforestation, cocaine trafficking, and destructive natural gas extraction. Nicholas Q. Emlen’s rich account—which takes us to remote Amazonian villages, dusty frontier towns, roadside bargaining sessions, and coffee traders’ homes—offers a new view of settlement frontiers as they are negotiated in linguistic interactions and social relationships. This interethnic encounter was not a clash between distinct groups but rather an integrated network of people who adopted various stances toward each other as they spoke. The book brings together a fine-grained analysis of multilingualism with urgent issues in Latin America today, including land rights, poverty, drug trafficking, and the devastation of the world’s largest forest. It offers a timely on-the-ground perspective on the agricultural colonization of the Amazon, which has triggered an environmental emergency threatening the future of the planet.