In 1851 the Mariposa Battalion came upon an unexplored valley in the Sierra Nevada while pursuing Native Americans. Lafayette Bunnell, a doctor who accompanied the battalion, kept a diary during the mission. They would be the first and last white men ever to see Yosemite unspoiled.
The documentary Yosemite: The Fate of Heaven was made in the late 80's and was part of the PBS series titled American Experience (season 2 episode 14). The film is narrated by none other than Robert Redford, in which he recites passages from Bunnell's diary. The film contrasts present-day Yosemite with Bunnell's experiences illustrating the devastation caused by millions of nature lovers. Enjoy the film!