U.S. environmental policy has reached a crossroads. Extraordinary progress has been made over the past half century in areas ranging from improving air and water quality to protecting valuable natural areas and wildlife. These and other accomplishments, however, have encountered a strong political backlash and episodic retrenchment. Environmental protection, once an issue with support across the political spectrum, has become mired in bitter partisanship and interest group competition. Moreover, important problems such as climate change, agricultural pollution, and racial and income disparities in environmental protection persist in a political system seemingly unable, or, at least, unwilling to respond. Academic researchers have played a key role in understanding the political, economic, social, and philosophical dimensions of U.S. environmental policy, and, given the complex problems still facing the country, have an even larger role to play going forward. This chapter provides an overview of U.S. environmental policy, and introduces the content of the Handbook.