What accounts for the remarkable growth of environmental sciences and studies (ESS) in US higher education over the past 50 years? This paper focuses on institutional characteristics to explain this 'long green wave' of expansion. Drawing on data from 1345 US higher-education institutions from 1980-2010, we employ three-level hierarchical models to assess institutional and state-level factors associated with the presence of environmental studies and sciences. Findings indicate that environmental studies majors are most likely to be present at liberal arts schools and in states more inclined to adopting environmentally friendly policies, and less likely to exist at schools with large minority enrollments. Environmental sciences majors are less likely to be present at schools with large female enrollments. Two case studies of early adopters highlight the role of faculty, rather than student activists, as change-agents pushing for the development of ESS on college campuses in the 1960s and 70s.