Silent Spring in 1962, which described the effects of DDT on the reproductive capabilities of birds, concern about the environment in the United States rapidly escalated in the 1960s. Catastrophic events such as a well-publicized fire on Ohio's Cuyahoga River and an oil spill in the Santa Barbara Channel gave additional momentum to the environmental movement. On December 2, 1970, President Richard Nixon signed the Environmental Protection Agency (EPA) into existence. Led by its first director, William D. Ruckelshaus, the EPA provided provided "a bite for the bark" of the recently passed environmental laws passed by Congress. Although continually challenged by various interests, the EPA and the laws it enforces are credited for greatly improving air, land, and water quality in the U.S.
Sources: Personal recollections and EPA.