Earth Day -- April 22 -- marks the anniversary of the birth of the modern environmental movement in 1970. It has been called “the largest secular holiday in the world” by Earth Day Network (EDN) – the non-profit organization that has promoted the event since its inception.

In 1970, the Environmental Protection Agency did not exist. The Clean Water Act and Endangered Species Act had not yet been written, and pollution was much more widespread in the U.S. than it is today.

On April 22, 1970, some 20 million Americans took to the streets, parks, and auditoriums to demonstrate for a healthy, sustainable environment.

Earth Day observations now occur in more than 190 countries.

Santa Barbara Oil Spill

Sen. Gaylord Nelson of Wisconsin was inspired to push for the first Earth Day event  after witnessing the aftermath of a huge oil spill off Santa Barbara, California in 1969. 

"The blowout was the spark that brought the environmental issue to the nation's attention," said Arent Schuyler, an environmental studies lecturer at the University of California at Santa Barbara in a 1989 interview with the Los Angeles Times.

"People could see very vividly that their communities could bear the brunt of industrial accidents. They began forming environmental groups to protect their communities and started fighting for legislation to protect the environment."