In the face of more than 20 years of experience in the USA, cities continue to search for ways of dealing with the fact that sustainability and its pursuit, as a matter of local public policy, is often deeply contested. This chapter examines the role of local environmental groups in this contestation with a particular eye toward understanding the role of such groups in the context of the underlying political ideology of cities. Taking advantage of patterns across 50 of the largest cities in the USA, this chapter examines the roles of pro-sustainability groups both in terms of their co-production activities and their advocacy before city government, and makes inferences about the importance of such groups independent of how progressive or conservative the city is. Consistent with mainstream understandings of the role of groups, this chapter argues that local decisions to try to become more sustainable are shaped by the roles played by environmental groups. It concludes with the suggestion that the pursuit of sustainability policies and programs moving forward will depend in large part on the extent to which environmental groups are willing and able to engage in advocacy before city policy-makers.