This article examines the future of the National Park Service Organic Act in a changing climate. Managers and scholars have raised questions about whether the Organic Act gives the Park Service sufficient authority to undertake the steps necessary to adapt to climate change. This article concludes that the Organic Act and park-specific enabling acts, as interpreted by the courts, grant the Park Service wide discretion to pursue management options for adaptation to climate change impacts on national park resources. It also concludes that the Organic Act, properly understood, does impose some necessary constraints on agency decision-making, constraints that prevent inappropriate development projects and that require thoughtful decision-making to minimize the risk of unintended management consequences. Overall, the Organic Act will remain relevant into the next century.