The assassination of rubber tapper union leader and environmental activist Chico Mendes in 1988 at his home in Xapuri, Brazil sent shockwaves through the international environmental conservationist community. Twenty years later in 2008, the massacre of 19 rural labor activists just kilometers away and across the Bolivian border hardly registered outside of Latin America. My dissertation traces the shared transnational historical roots of Mendes' assassination and the Porvenir Massacre on both sides of the Bolivia/Brazil border. I argue that this recent rural violence has roots in the rubber boom (1850-1920), when rubber barons used a combination of debt bondage and physical coercion to secure labor from rubber tappers. In spite of social, political, and economic changes between the 1920s and 1980s, this underlying structure of subjugation remained in place, and regional elites' perceived right to control peasant bodies has manifested itself in outbursts of brutal violence ever since. My study's focus on transnational processes such as trade, political and cultural influence, migration, and ecological events such as floods and droughts calls for new understandings of Amazonia beyond national borders. Meanwhile, elucidating the effects of both countries' national developments on this international space provokes a rethinking of the way we understand the both the functions and limitations of the nation in the region. This research also has important implications for environmental conservationist thought and policy; by blending political ecology and social history in the study of a group connected to environmental struggles, I show that conservationists must first understand the historical dimensions of the human-environment relationships into which they seek to intervene.