The Nelson Collection (http://www.nelsonearthday.net/collection/) is preserved in the archives of the Wisconsin Historical Society. A selection of key documents and images is located in this website, and offers an unprecedented look into the creation and legacy of Earth Day, the political battles of 1960s and 1970s environmentalism, and the heyday of postwar liberalism.
Opened to researchers in 2008, the Nelson Collection at the Wisconsin Historical Society contains over 250 boxes of material from Gaylord Nelson's career in the Senate, his subsequent tenure as Counselor of The Wilderness Society, and as one of the most prominent environmentalists in the United States.