Over the last 5 years, the U.S. Congress has voted on several pieces of legislation intended to sharply reduce the nation's greenhouse gas emissions. Given that climate change is a world public bad, standard economic logic would predict that the United States would “free ride” and wait for other nations to reduce their emissions. Within the Congress, there are clear patterns to who votes in favor of mitigating greenhouse gas emissions. This paper presents a political economy analysis of the determinants of “pro-green” votes on such legislation. Conservatives consistently vote against such legislation. Controlling for a representative's ideology, representatives from richer districts and districts with a lower per-capita carbon dioxide footprint are more likely to vote in favor of climate change mitigation legislation. Representatives from districts where industrial emissions represent a larger share of greenhouse gas emissions are more likely to vote no. (JEL Q54, Q58, R50)