EPA's Earth Day Site
"On April 22, 1970, 20 million people across America celebrated the first Earth Day. It was a time when cities were buried under their own smog and polluted rivers caught fire. Now Earth Day is celebrated annually around the globe. Through the combined efforts of the U.S. government, grassroots organizations, and citizens like you, what started as a day of national environmental recognition has evolved into a world-wide campaign to protect our global environment. Learn about the history of Earth Day. Más información en español..."