Earth Day was first observed in Spring of 1970. An estimated 20 million people nationwide attended festivities out of which came the largest grassroots environmental movement in U.S. history, and the impetus for national legislation like the Clean Air and Clean Water Acts. By the twentieth anniversary of that event, April 22, 1990, more than 200 million people in 141 countries participated in Earth Day celebrations.
Earth Day is not without historical precedent. Both Arbor Day and Bird Day were established in the late 1800s to support forestation, conservation, and the appreciation of nature. Native American peoples have long recognized and celebrated in story and song the interdependence of the earth and all her creatures.