Earth Day is celebrated every year on April 22. Senator Gaylord Nelson proposed the first Earth Day in 1970 as a way to teach people about the importance of protecting the environment.
For more information, see EPA's Earth Day site
You may also wish to visit the "Earth Day Network" Web site, where you can learn more about events that are being held around the United States and the rest of the world. The Earth Day Network is the nonprofit coordinating body of worldwide Earth Day activities.
See: Earth Day Network