Earth Day is celebrated annually on April 22nd to promote environmental protection. It was founded in 1970 by US Senator Gaylord Nelson as an environmental teach-in in response to growing pollution, including an oil spill in California in 1969 and a river catching fire due to waste in Ohio. On the first Earth Day in 1970, approximately 20 million Americans participated in demonstrations across the country to demand action on protecting the environment. Earth Day has since grown into a global event observed in over 190 countries each year.