This book examines the environmental history of the Antarctic Peninsula region from the early twentieth century to the present. As the most politically contested part of the Antarctic continent, the Antarctic Peninsula region is a good location for considering the intersection of diplomatic history and environmental history. In making imperial claims to the Falkland Islands Dependencies, British officials argued that the production of useful scientific knowledge about the Antarctic environment helped to justify British ownership. In contrast, Argentines and Chileans made the case that the Antarctica Peninsula belonged to them as a result of geographical proximity, geological continuity, and a general sense of connection. Despite being caught up in the broader struggles between imperialism and nationalism of the mid-twentieth century, the Antarctic Peninsula region was never decolonized. Instead, under the terms of the 1959 Antarctic Treaty, existing sovereignty claims and reservations of rights were frozen for the duration of the treaty, and the whole Antarctic continent came to be governed by a treaty system that drew much of its authority from the production of useful scientific knowledge. In making an argument for imperial continuity in the history of the Antarctic Peninsula region, an environmental history approach offers a new perspective on the history of Antarctica that suggests that the environment, science, and politics continue to be closely entwined. This in turn has important implications for thinking about connections between diplomatic history and environmental history in different parts of the world and in addressing pressing global challenges such as climate change.