A self-defined sustainability movement crystallized between the late 1970s and the 1990s. No longer was sustainability merely a concept or set of ideas. There was now a set of organizations—the Worldwatch Institute, the Rocky Mountain Institute, the United Nations (UN ), and so on—that promoted something called “sustainability” and a growing number of individuals who sought to “live sustainably.” Scholars began to describe in vivid detail what a sustainable society might look like and discussed in no uncertain terms the unsustainability of modern industrial society. In 1975, a conference was held near Houston, Texas, on “how a modern society might be organized to provide a good life for its citizens without requiring ever-increasing population growth, energy resource use, and physical output.” A stream of books between 1976 and 1981 drew on cutting-edge science and ecological economics to sketch out the “qualitative components of a sustainable society.” In the 1980s, sustainability became the centerpiece of international agreements; a strategy objective for at least some nongovernmental organizations (NGOs), businesses, and governments and a philosophy of balance and durability with a wide range of applications. It found its greatest champion in the United Nations though, which recast sustainability as “sustainable development” and integrated its principles into international accords. Sustainability had thus become part of a political agenda and a clearly articulated ecological philosophy, and a plethora of frameworks, systems, and models were developed as a means of studying, measuring, and advancing its central tenets. This is the period, for instance, in which the three Es appeared as the basic model for sustainability. By the 1990s, sustainists had begun implementing principles of sustainability into economic analyses, planning commissions (on all governmental levels), the energy sector, education, agriculture, housing, transportation, business operations, and many other domains. The media picked up on the term, too, and sustainability became, by the end of the century, a buzzword meant to signify anything associated with green values. This chapter offers a brief overview of the formation, triumphs, and challenges of the sustainability movement at the end of the twentieth century.