April 22nd marks the 40th anniversary of Earth Day, a national event that was started by the late Senator Gaylord Nelson. Nelson captured the fervor and national sense of social activism of the 1960s to push an environmental agenda in Congress and around the country. Bill Christofferson wrote a biography of Gaylord Nelson called The Man From Clear Lake. He talks with host Steve Curwood about Nelson’s life and legacy as an environmentalist before his time.