In the decades leading up to the first, Americans were consuming vast amounts of leaded gas through massive and inefficient automobiles. Industry belched out smoke and sludge with little fear of the consequences from either the law or bad press. Air pollution was commonly accepted as the smell of prosperity. Until this point, mainstream America remained largely oblivious to environmental concerns and how a polluted environment threatens human health.
However, the stage was set for change with the publication of Rachel Carson’s New York Times bestseller Silent Spring in 1962. The book represented a watershed moment, selling more than 500,000 copies in 24 countries as it raised public awareness and concern for living organisms, the environment and the inextricable links between pollution and public health.

Senator Gaylord Nelson, the junior senator from Wisconsin, had long been concerned about the deteriorating environment in the United States. Then in January 1969, he and many others witnessed the ravages of a massive oil spill in Santa Barbara, California. Inspired by the student anti-war movement, Senator Nelson wanted to infuse the energy of student anti-war protests with an emerging public consciousness about air and water pollution. Senator Nelson announced the idea for a teach-in on college campuses to the national media, and persuaded Pete McCloskey, a conservation-minded Republican Congressman, to serve as his co-chair.

Senator Gaylord Nelson recruited Denis Hayes, a young activist, to organize the campus teach-ins and to scale the idea to a broader public, and they choose April 22, a weekday falling between Spring Break and Final Exams, to maximize the greatest student participation.

Recognizing its potential to inspire all Americans, Hayes built a national staff of 85 to promote events across the land and the effort soon broadened to include a wide range of organizations, faith groups, and others. They changed the name to Earth Day, which immediately sparked national media attention, and caught on across the country. Earth Day inspired 20 million Americans — at the time, 10% of the total population of the United States — to take to the streets, parks and auditoriums to demonstrate against the impacts of 150 years of industrial development which had left a growing legacy of serious human health impacts.