To tell the story, we need to (a) consult the University of Wisconsin’s Nelson Institute for Environmental Studies, and (b) travel back to Sept. 20, 1969, when, during a speech to “a fledgling conservation group in Seattle,” Sen. Gaylord Nelson proposed that the United States hold “a national teach-in on the environment to send a message to Washington that public opinion was solidly behind a bold political agenda on environmental problems.” He repeated the idea “six days later in Atlantic City to a meeting of the United Auto Workers.” The idea picked up steam, became the first Earth Day on April 22, 1970, and eventually spread around the world.