The last decade has seen an upsurge of both scholarly and popular interest in the US environmental justice movement. What is largely missing from this contemporary discussion is any sense of the historical roots of this new wave of environmental activism. This paper explores the emergence of a radical Puerto Rican organization called the Young Lords that was active in a number of US cities in the late 1960s and early 1970s. In New York City, the Young Lords successfully mobilized their community through a series of direct actions devoted to improving public services, the creation of new community spaces and the assertion of cultural identity. I examine the internal tensions within the organization as it sought to extend its role beyond community-based concerns such as sanitation and health care towards more abstract political goals, including demands for Puerto Rican independence. It is argued that the ultimate disarray of this radical phase of Latino political activism cannot be understood separately from a series of wider developments, including the gathering pace of urban decline, the marginalization of the US left and the dissolution of the New Deal era. Although the movement faded away in the 1970s, a legacy of diasporic environmentalism dedicated to the transformation of the urban environment has provided a powerful degree of political continuity with contemporary struggles for environmental and social justice.