The Environmental Movement in the United States gained significant momentum in the decades following World War II, driven by increased awareness of pollution and the degradation of natural resources. One of the key legislative achievements of this movement was the establishment of Earth Day in 1970, which reflected a growing public concern for environmental issues. Additionally, the movement led to the creation of several important regulations aimed at protecting the environment. Which of the following pieces of legislation is most closely associated with the start of the modern Environmental Movement in the U.S.?