In 1864, Congress passes an act that protects California's Yosemite Valley; in 1872, Congress passes an act to protect a part of Wyoming, which becomes America's first national park -- Yellowstone.

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.

The automobile allows more people than ever to visit the national parks; campaign to protect the remaining virgin forest in the Smoky Mountains.

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.