A quote from the piece in Smithsonian Magazine of the above title:
As a young man, Muir felt he was a student in what he called the ‘University of the Wilderness,'" Gisel said. "Yosemite was his graduate course. This is where he decided who he was, what he wanted to say and how he was going to say it."
When he first strode into Yosemite in the spring of 1868, Muir was a scruffy Midwestern vagabond wandering the wilderness fringes of post-bellum America, taking odd jobs where he could. In retrospect, visiting Yosemite might seem an inevitable stop on his life's journey. But his later recollections reveal a young man plagued with self-doubt and uncertainty, often lonely and confused about the future. "I was tormented with soul hunger," he wrote of his meandering youth. "I was on the world. But was I in it?"