The US national park system includes 423 sites covering more than 85 million acres of land and some of the most iconic landscapes in the country. The parks host approximately 320 million visitors a year. In this review, I survey the economics literature on national parks, focusing on four main topics: values and economic impacts of the parks, funding challenges, congestion and overcrowding, and resource management issues related mainly to climate change. In each area, I discuss gaps in the literature, new data and methods that could be applied to national parks, and important topics for future research. The most pressing needs are for more empirical research on use values, using new data sources and modern econometric methods, and relatedly, studies of the responsiveness of demand to pricing, which would be helpful for addressing both congestion and funding challenges. Expected final online publication date for the Annual Review of Resource Economics, Volume 14 is October 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.