John Muir was one of the nation's most eminent nature writers, a father of our national parks, and a keen advocate for keeping unmanaged nature alive. The impact of his articles in Century magazine in the late 1880s drew attention to the destruction of forestland by grazing animals, and eventually led to the creation of Sequoia and Yosemite national parks in 1890.
Shortly thereafter, Muir recognized the importance of establishing an organization that could serve as a sounding board for his ideas, that could develop others who would lead as he had led and that could build with its numbers a political force of his own. He founded the Sierra Club.
One night in 1903, Muir camped with President Theodore Roosevelt in a remote spot in Yosemite, much to the consternation of Roosevelt's retinue. They rode down the trail past Vernal and Nevada Falls to the Valley, and then rejoined Roosevelt's formal group the next day. Historians speculate that that evening gave Muir just the opportunity he needed to persuade Roosevelt to establish the U.S. Forest Service, which the President did two years later.
Through his inspirational writing and the sheer power of his advocacy, John Muir made a big difference in motivating a nation and its leaders to conserve the natural world.