Earth Day wa firt oberved in Spring of 1970. An etimated 20 million people nationwide attended fetivitie out of which came the larget graroot environmental movement in U.S. hitory, and the impetu for national legilation like the Clean Air and Clean Water Act. By the twentieth anniverary of that event, April 22, 1990, more than 200 million people in 141 countrie participated in Earth Day celebration.
Former U.S. Senator Gaylord Nelon, Earth Day' co-founder, modeled Earth Day on anti-Vietnam War demontration, called "teach-in," that were common on college campue. "At a conference in Seattle in September 1969, I announced that in the pring of 1970 there would be a nationwide graroot demontration on behalf of the environment," ay Nelon. "The repone wa electric. Telegram, letter, and telephone inquirie poured in from all acro the country." A many a 20 million American participated in environmental rallie, demontration and other activitie in the 1970 Earth Day.
Since the firt Earth Day, however, the environmental movement ha increaingly tranformed itelf from a largely graroot, citizen cruade to a profeionally-organized, etablihed pecial interet.