Senator Gaylord Nelson has explained the origins of Earth Day:
At a conference in Seattle in September 1969, I announced that in the spring of 1970 there would be a nationwide grassroots demonstration on behalf of the environment and invited everyone to participate. The wire services carried the story from coast to coast. The response was electric. It took off like gangbusters. Telegrams, letters, and telephone inquiries poured in from all across the country.The American people finally had a forum to express its concern about what was happening to the land, rivers, lakes, and air – and they did so with spectacular exuberance. For the next four months, two members of my Senate staff, Linda Billings and John Heritage, managed Earth Day affairs out of my Senate office.
We still don’t understand why environmentalism took hold the way it did, resulting in a wave of environmental legislation in the following decade. It is clear, however, that Earth Day was tapping into a reservoir of public concern:
Earth Day worked because of the spontaneous response at the grassroots level. We had neither the time nor resources to organize 20 million demonstrators and the thousands of schools and local communities that participated. That was the remarkable thing about Earth Day. It organized itself.