Environment and climate change data that has been deleted from government site has been rescued (and is continued to be checked each year). Check the datasets for material desired for classes or reports.
The American Memory Project from the Library of Congress covers documents here from the Conservation Movement from 1847 - 1920. As early as 1847, with the speech of Charles Perkins Marsh to the Agricultural Society about the impact of human activity on the environment, a movement was begun to create new ways to work. Engage your students by sharing these diverse documents from speeches, to essays, to photographs and proposed Bills to Congress - how have we progressed and what work still needs doing?
the Online Archive of California points us to the John Muir Correspondence housed at the Bancroft Library at U.C. Berkeley. There are some digitized letters that can be viewed as part of research into his life as well as his views on nature and the environment.
Using this interactive map and the resources from the National Archives and the Environmental Protection Agency (EPA) DOCUMERICA Project of the 1970's, this lesson shows the environment as it was when the EPA began.