Viewpoint author Denis Hayes (pictured in 1970) has been leading international Earth Day events since he coordinated the first Earth Day in 1970.
Photo courtesy AP Wide World Photos
Earth Day 2000 in Washington, D.C.
Photo courtesy Earth Day Network
About half a million people attended events for Earth Day 2000 on the National Mall in Washington, D.C.
EARTH DAY NETWORK
Denis Hayes in 2004.
Photo courtesy Inye Wokoma
Environmentalists carry an Earth flag through the streets of Boston on Earth Day 1970.
Photo courtesy Ivan Massar
Raise the flag! Earth Day celebration, 2000.
Photo courtesy Aneal Vohra