This article examines the collision of crude oil and mangroves in the Caribbean during the 1970s as one regional facet of a larger dialectic of hydrocarbon risk and environmental responsibility. Such a collision, I argue, offers a striking account of how the agency of the natural world became intelligible within the modern project. Beginning with the pivotal but often neglected place of petroleum in the Caribbean, I show how crude oil is still something that requires some explanation in the region. Using the local history of what became the largest refinery in the Western Hemisphere—the mammoth scale of this St. Croix refinery is dwarfed only by its neglect in popular and scholarly accounts of the region—I describe how fossil fuels were introduced to one colonial territory in the Caribbean and the social and environmental consequences of that introduction.1 Over a dozen export-oriented refineries were built by U.S. oil companies in a similar fashion across the Caribbean between 1950 and 1970. As the United States moved significant portions of its hydrocarbon infrastructure offshore, the region became the world’s largest exporter of refined petroleum products in the world, almost all of which went to the United States (United Nations 1980). Between 1950 and 1990, oil refineries became the largest site of capital investment in the Caribbean, a leading source of state revenue, and one of the region’s largest employers, especially during the construction boom of refineries in the late 1960s and early 1970s (United Nations 1979; World Bank 1984; Richardson 1992). These events stand at odds with other accounts of what makes the Caribbean a unique and enduring cultural region. As the sugar plantation became the defining image of the Caribbean for critical scholars and national leaders alike, the expanding energy networks of the United States underwrote much of the area’s contemporary aspirations.