In the summer of 1869, Scottish-American naturalist and authorJohn Muirspent the months of June through September in the Sierra Nevada Mountains of California accompanying a group of shepherds while they led a flock of sheep to the high country to graze. During that time, Muir took every opportunity to explore the Yosemite area extensively—hiking, camping, writing, and sketching. Muir’s diary entries describing the land, flora, and fauna he encountered became...