This Article explains how and why development emerged as a conceptual framework, the basic concepts or principles on which this framework is based, why sustainability is primarily a matter for domestic national governance, and why the United States needs to play a leading role in fostering development. Because sustainable modifies it is first important to understand what development means. Since the end of World War II, development has included at least four related elements: peace and security, economic development, social development, and supportive national governance. Each element is reflected in major multilateral treaties that provide a common framework for relations among sovereign nations as well as a shared set of national purposes. These elements together are intended to foster human quality of life and opportunity. While the development model has been successful on its own terms, it has not addressed or prevented two related problems - environmental degradation or the large number of people living in poverty. Sustainable development modifies the traditional development model by adding a fifth element, protection of the environment, but the idea of fostering human quality of life and opportunity remains the same. Key principles include integration of the environment into decision making, the polluter-pays principle, the precautionary principle, intergenerational equity, public participation, and common but differentiated responsibilities for developed and developing countries. Because of national sovereignty, development is primarily the responsibility of national governments. While environmental and conservation laws provide a foundation for development, they do not reflect the range or depth of necessary actions, nor are they necessarily the most economically efficient means of achieving development. The United States should play a leading role in addressing development because of the contribution it has made to global environmental challenges and because of its enormous potential capability to address these challenges.