Increasing concerns over climate change and volatile energy prices have led several state governments to consider legislation to mitigate these matters. At the state level, Renewable Portfolio Standards (RPS) have emerged as a popular tool to motivate the transition away from fossil fuels, reduce carbon emissions, and diversify electricity supply. This study examines the economic, social, and political factors that prompt a state to adopt a Renewable Portfolio Standard. A fifty-state panel data set over the years 1990–2010 was assembled from the United States Energy Information Administration, Bureau of Economic Analysis, the Database of State Incentives for Renewables and Efficiency (DSIRE), and state legislative data from Indiana State University. Using the data set complied for this study, I estimate a probit model to determine the probability a state will adopt an RPS in a year given its present political and economic climate. Results show that a deregulated electricity market, a high per-capita GDP, a strong democratic presence in the state legislature, high renewable capacity, and a strong incidence of natural gas are indicators a state will pass an RPS. Whether or not a state is a net importer or exporter of electricity is not a significant indicator of adoption of an RPS within a state.