In 1851, Yosemite's beauty draws those seeking profit and those, like John Muir, who see its protection as a calling. In 1864, Congress passes a historic act preserving Yosemite for public use, marking the first time a government protects land from commercial development. Control is given to California, laying the groundwork for future conservation efforts.

Yellowstone's unique geysers and landscapes attract visitors, leading Congress to protect it in 1872 as America’s first national park. Since it's in a territory, not a state, federal control is established. Meanwhile, John Muir campaigns to preserve California's Sierra Nevadas as a national park, furthering the movement for land conservation.

By the late 19th century, industrialization threatens America's wilderness, while poaching and vandalism plague the parks. With no clear legal protections, a conservation movement emerges. John Muir's Sierra Club, George Bird Grinnell's Audubon Society, and Theodore Roosevelt's Boone and Crockett Club push for stronger preservation efforts to safeguard the nation's natural treasures.

After a camping trip together, Theodore Roosevelt and John Muir join forces to protect more American landscapes as national parks; but they part ways when Muir fights the battle of his life to save a beautiful valley.

In John Muir's absence, a new leader steps forward on behalf of America's remaining pristine places; a new federal agency is created to protect the parks; and new parks are created in Hawaii and northern Montana.

Stephen Mather pushes his new agency to add parks in Alaska, the coast of Maine, and southern Utah; and in Arizona, a fight breaks out over the fate of the grandest canyon on earth.

As America embraces the automobile, a Nebraska housewife searches for peace and inspiration in park after park, and the future of the Great Smoky Mountains becomes caught in a race with the lumbermen's saws.

A honeymoon couple seeks fame and adventure in the Grand Canyon; and the richest man in America sets out to save the Great Smoky Mountains of the Southeast and then Wyoming’s spectacular Tetons.

In the midst of an economic catastrophe, the national parks provide a source of much-needed jobs; the park idea changes to include new places and new ways of thinking.

During World War II, the national parks provide a source of peace to battle-weary soldiers and a source of poignant memory to some Japanese Americans imprisoned unfairly; President Roosevelt fights pitched battles against special interests to create new parks in the West.

After World War II, American families flock to their parks in unprecedented numbers, creating new problems of overcrowding but also passing on a love of the parks to the next generation. In Alaska, a stubborn iconoclast fights a lonely battle on behalf of a species nearly everyone hates.

The last string of unspoiled islands south of Miami is saved with the help of the son of a former slave; and in Alaska, America's "Last Frontier" becomes a testing ground for the future of the park idea.