Following the American Civil War in the summer of 1869, John Muir signed on with a crew of shepherds to drive a flock of 2500 sheep to Yosemite National Park at the headwaters of the Merced river. It wasn't until 1911, however, that he published "My First Summer in Sierra," an account of that experience which would inspire many to visit the Yosemite region and has become a classic of environmentalist literature.