As environmental values increasingly become religious values within mainstream American religions, what kinds of tensions arise in the negotiation of tradition, environmental ethics, and a popular religious practice that combines them both? What insights can be gained into the processes of religious reinterpretation and renewal by examining the making a new ecological religious culture within an historic Christian institution? In The Greening of American Catholicism, I reveal a growing movement of Catholic communities in America, which are redefining their religious identity, theology, and practice in terms of an environmental ethic. Founded by Dominican Sisters Miriam MacGillis, Genesis Farm has become a leading force in the creation of a new American Catholic Ecology. Data from my three years of ethnographic study of Genesis Farm and nearly a dozen similar communities brings to light the growth and development of a nexus between Catholicism and environmental ethics on the level of practice that provides an ideal venue for better understanding the dynamics of a rapidly shifting American religious and cultural landscape.