and other images were captured in the 70s, commissioned by the Nixon administration in conjunction with the creation of the EPA, for a project called Documerica. The National Archives have recently been making photos from the collection available.
A couple of days ago, Wired Science published a selection of these photos, and you can search the archives at the National Archives (you might want to use the search instructions at the Documerica site at the Knight Center for Environmental Journalism).