Today is the 173rd birthday of John Muir. If the legacy of wildland preservation in this country were a river long with oxbows, falls and many notable tributaries, Muir's contributions would certainly be the headwaters.

Muir was the co-founder and first president of the Sierra Club and a steadfast advocate for the protection of wilderness. Through his essays and books—penned late in life after years of exploration—he has exposed millions to the wonders of the outdoors, and particularly the many rewards that await the California mountaineer. But Muir's greatest gift to me is the encouragement given to put the book down and go out and do: "Only those will ever know who give the freest and most buoyant portion of their lives to climbing and seeing for themselves," he wrote in The Mountains of California.

It was in the spring of 1868 that this wide-eyed son of a Scottish minister first came by wanderlust into California's Sierra Nevada mountains—or the Range of Light as he called it—to see for himself. As he climbed into the Yosemite Valley, Muir discovered the towering granite buttresses that would become the rocks of his own church.

In the years following, he conducted his ministry in the river valleys and high country of the Sierra with a passion and enthusiasm that were as powerful a force as the grinding glaciers that carved his mountain home. He spent years dutifully investigating and cataloguing its inhabitants, and not just the living ones. Muir also spent considerable time enumerating the region's glacier lakes—which in today's warming world are like the fingerprints left by large hands of molding ice that have mostly vanished from the scene.

Earlier this week, PBS aired a 90-minute special called "John Muir in the New World." If you didn't catch it then, you can still watch it online. It's a wonderful introduction to the life and passions of a man whose words have carried me into the California wilderness time and again.

From The Mountains of California: "We always find that the strangest objects in these fountain wilds are in some degree familiar, and we look upon them with a vague sense of having seen them before… for going to the mountains is like going home."

Happy Birthday, Mr. Muir.

Some more photos from Yosemite National Park, the heart of John Muir's world: