Which major environmental legislation was passed in the U.S. during the 20th century?

The Clean Air Act is a significant piece of environmental legislation passed during the 20th century that aimed to regulate air emissions from stationary and mobile sources. Initially enacted in 1963, it was majorly amended in 1970 and again in 1990, strengthening the government’s ability to protect public health and the environment from air pollution. The Act establishes National Ambient Air Quality Standards (NAAQS) for six principal pollutants and provides the framework for state implementation plans to achieve and maintain these standards.

The success of the Clean Air Act is evident in the significant reduction of air pollutants and improvements in air quality across the United States, which has had lasting public health benefits. It also spurred economic growth within the environmental sector by promoting cleaner technologies and alternative energy sources. The Act serves as a critical piece of the United States' environmental regulatory framework, demonstrating the government’s commitment to mitigating the impacts of pollution on human health and the environment.

The other options represent important environmental laws as well; however, they address different aspects of environmental protection. For example, the Clean Water Act focuses specifically on water pollution, while the Endangered Species Act aims to protect threatened and endangered species and their habitats. The National Environmental Policy Act (NEPA) requires federal agencies