EPA: "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."

• Calculate your carbon footprint
  
• learn how you can use more efficiently
  
• learn more about recycling
  
• check the air quality in your area on interactive maps
  
• Library of Congress Science Reference Guides - Earth Day