On a May morning in 1903 two men pose for a photograph at Glacier Point, above Yosemite Valley in the heart of the Sierra Nevada of California. They have slept the night in the open and have woken under a blanket of four inches of snow. The man dressed in the knickers and neckerchief of an outdoorsman is the president of the United States, Theodore Roosevelt. He has requested a camping meeting with the famous wilderness sage, John Muir, who hopes to persuade the president to take jurisdiction for the valley itself away from the state of California and into the wider Yosemite National Park that Muir had been instrumental in creating in 1892. Characteristically, Muir used camping out as a form of lobbying on behalf of a landscape that he wished to see preserved for future generations to enjoy.

The notion of the national park system is credited to...