In 1851, word spread of California’s beautiful Yosemite Valley, attracting visitors who wished to exploit the land for commercial gain as well as those who wished to keep it pristine. This episode relates how a Scottish-born wanderer named John Muir made protecting this land a spiritual calling. In 1864, Congress passed an act that protects Yosemite from commercial development—the first time in history that any government put forth such an idea.