Laurence I. Moss (1935-1999) was a nuclear engineer and consultant on environmental and energy policy. This oral history focuses on his role in the Sierra Club in the 1960s and 1970s. He gave key testimony in the House Interior Committee in 1966, defending the club’s position against plans to build dams in the Grand Canyon for energy production. Moss helped the club undercut economic rationales for the dams, arguing that nuclear power would be more cost-effective. In 1968 he was elected to the Sierra Club Board of Directors and in 1973 the board chose him as the first non-Californian to serve as Sierra Club president. As president, Moss focused on overcoming serious budget deficits, improving management information and control systems, and establishing clear program priorities. Ironically, it was during his term as president that the board of directors was persuaded, with strong support from the club chapters and grassroots activists, to declare its support for a moratorium on nuclear power plants. In the oral history, Moss expresses his regret at the failure of the board to subject the decision to a rigorous analysis of costs, risks, and benefits of nuclear vis-à-vis alternative energy technologies. The oral history also discusses Moss’s contributions to the fight against the Supersonic Transport and to national energy policy in the 1970s, including the Clean Air Act legislation and the National Coal Policy Project. In later years he became an advocate for market-based solutions to environmental problems, as opposed to increased government regulation.