Earth day was founded in 1970 by Senator Gaylord Nelson, but only after several years in the planning. Frustrated that the environment was a “non-issue” in politics in the 1960s, Senator Nelson flew to Washington, and presented an idea that both the then Attorney General, Robert Kennedy, and then President, John F. Kennedy, both liked. What ensued from that meeting was a “five-day, 11-state conservation tour in September 1963″ by President Kennedy. (The tour took place a mere two months before he was assassinated.)
After several years speaking throughout the country on the environmental degradation he saw all around him, and spurred on by “teach-ins”, the anti-Vietnam war protests taking place across the U.S., Nelson finally hit upon his idea – create “a huge grassroots protest over what was happening to our environment[.]”
With “neither the time nor resources to organize 20 million demonstrators,” Nelson, his senatorial staff and dozens of volunteers, including “thousands of schools and local communities” brought together an American public just waiting for a platform to voice their concerns about the environment. Nelson said, “That was the remarkable thing about Earth Day. It organized itself.” 
After 40 years, Earth Day has organized itself into 77,862,183 people having pledged to do their part to help planet earth.
Headline image from EarthDay.org
 All information and quotes from Senator Gaylor Nelson in “How The First Earth Day Came About” published on Earthday.Envirolink.org.