When was the first Earth Day?

Earth Day was proposed by US Senator Gaylord Nelson after a massive oil spill off Santa Barbara, California, in 1969. Organised with activist Denis Hayes, the first Earth Day on 22 April 1970 brought an estimated 20 million Americans onto streets, campuses and parks, around a tenth of the US population at the time. The public pressure helped lead to the creation of the US Environmental Protection Agency later that year and to laws such as the Clean Air Act. Earth Day went global in 1990, mobilising about 200 million people in 141 countries. Today it is marked every 22 April in more than 190 countries.