On Earth Day 1970 twenty million Americans displayed their commitment to a clean environment. It was called the largest demonstration in human history, and it permanently changed the nation's political agenda. More than one billion people now participate in annual Earth Day activities. The seemingly simple idea - a day set aside to focus on protecting our natural environment - was the brainchild of U.S. Senator Gaylord Nelson of Wisconsin. It accomplished, far beyond his expectations, his lifelong goal of putting the environment onto the nation's and the world's political agendas. The life of Nelson, a small-town boy who learned his values and progressive political principles at an early age, is woven through the political history of the twentieth century. Nelson's story intersects at times with Fighting Bob La Follette, Joe McCarthy, and Bill Proxmire in Wisconsin, and with George McGovern, Lyndon Johnson, Hubert Humphrey, Russell Long, Walter Mondale, John F. Kennedy, and others on the national scene.