Climate and energy policy needs to be durable and flexible to be successful, but these two concepts often seem to be in opposition. One venerable institution where both ideas are apparent is the Clean Air Act, first passed by the United States Congress in 1963, with amendments in 1970 and 1990. The Act is a living institution that has been hugely successful in improving the environment. It has programs that reach across the entire economy, regulating various sectors and pollutants in different ways. This illuminating book examines these successes - and failures - with the aim to offer lessons for future climate and energy policymaking in the US at the federal and state level. It provides critical information to legislators, regulators, and scholars interested in understanding environmental policymaking.