Scholars working on global environmental change research are increasingly seeing the value of collaborating on projects involving methodologies in the geophysical sciences and humanities to solve environmental problems such as climate change, soil erosion, and loss of biodiversity. Largely missing from these works, however, are histories of what might be considered earlier interdisciplinary scholarship by physical and human geographers, which are valuable for thinking about what it means to practice the interdisciplinary study of the environment. The purpose of this paper is to examine the understudied history of McGill University's Caribbean Project of the 1950s and 1960s, to consider what it might tell us about the histories of interdisciplinarity in (geographical) research. We seek to broaden understandings about the very nature of interdisciplinarity, including what may be called early exercises in critical physical geography, through an examination of this small but important and enduring Canadian program located in Barbados with its own complex historical geographies. Focusing on a few instrumental scholars involved in the Barbados project—including the climatologist Kenneth Hare, the cultural geographer Theo Hills, and the biogeographer David Watts—our contribution draws on primary materials (correspondence, reports, memoranda, and research site plans) obtained through the McGill University Archives and the Bancroft Library at Berkeley University, as well as close readings of McGill Geography's digitized Climatological Bulletins (1967–93), Climatological Research Series, and student theses and dissertations. We conclude by suggesting possible ways forward for future interdisciplinary research on this and other projects, involving physical and human geographers and historians as well as local participants.