In what year was the first Earth Day held?

The first Earth Day was held in 1970, specifically on April 22. Senator Gaylord Nelson proposed a nationwide environmental teach-in after seeing how effectively civil-rights and antiwar teach-ins could mobilize public attention. Harvard graduate student Denis Hayes became the campaign’s national coordinator and helped turn the proposal into a broad movement.

The 1970 event was initially focused on the United States. Activities took place at roughly 2,000 colleges and universities, about 10,000 primary and secondary schools, and hundreds of communities. Estimates commonly put participation at around 20 million Americans, making it one of the largest public demonstrations in U.S. history at that time.

A frequent source of confusion is that another Earth Day tradition is associated with the March equinox. Activist John McConnell proposed an equinoctial observance in 1969, and a March 21, 1970, event was held in some places. However, the Earth Day that became the major annual international observance is the April 22 event launched in 1970. Earth Day later expanded internationally, especially after 1990.