In 1849, 11-year-old John Muir emigrated from Scotland to America. Here, he rose from farmer and sawmill worker to become a noted authority on the botany, glaciers, and forestry of the nation's wilderness. Best known for his long association with the Yosemite Valley and Sierra Nevada Mountains of California, Muir also explored, mostly afoot, the southern states, Alaska, the Great Basin, and the Mojave Desert. His studies took him around the world and generated volumes of poetic, evocative writings. As America expanded relentlessly westward, Muir witnessed the plunder and exploitation of the land and became a driving force in efforts to protect the natural world. A modest and private man, married and father of two daughters, his conservationist views forced him into battle with powerful political and industrial interests. He influenced four U.S. Presidents to sponsor legislation that protected forests and established or expanded America's national parks.