In 1851, word spreads across America of a beautiful area of California's Yosemite Valley attracting visitors who wish to exploit the land's scenery for commercial gain and those who wish to keep it pristine. Among them is John Muir for whom protecting the land becomes a spiritual calling. In 1864, Congress passes an act that protects Yosemite from commercial development and hands control of the land to California.

President Theodore Roosevelt champions the national parks; conservation movement fails to prevent the building of the Hetch Hetchy dam at Yosemite.

The National Park Service is established in 1916; Stephen Mather campaigns to establish the Grand Canyon in Arizona as a national park.

While visiting the parks was once predominantly the domain of Americans wealthy enough to afford the high-priced train tours, the advent of the automobile allows more people than ever before to visit the parks. Stephen Mather embraces this opportunity and builds more roads in the parks.

The national parks provide a source for jobs and peace; the park idea expands to include new places and new ways of thinking.

Biologist Adolph Murie believes predatory animals deserve to be protected; in 1995, wolves are re-established in Yellowstone National Park.