In December of 1974, Mexico’s president, Luis Echeverría, stood before the General Assembly of the United Nations to present the founding principles of what was to be a New International Economic Order, a project intended to address the economic crisis then wracking the Third World. The principles that the Mexican president imagined were codified a document that Echeverría had been drafting over the previous two years, the Charter of Economic Rights and Duties of States. This chapter traces this advocacy to discover the Mexican roots of the New International Economic Order, and in so doing demonstrates how Mexican diplomats, economists, and policymakers shaped not only ideas about sovereignty, self-determination, and economic development during the twentieth century, but also the codification of those ideas in international law, agreements, and institutions.