Gaylord Nelson was an American politician born in 1916 in Wisconsin who is best known for founding Earth Day. He served as a U.S. Senator from 1963 to 1981, championing numerous environmental causes. In 1962, Nelson began developing the idea of an environmental teach-in, which materialized on April 22, 1970 as the first Earth Day. Earth Day engaged 20 million Americans and is credited with launching the modern environmental movement. Nelson continued advocating for the environment until his death in 2005 at age 89.