John Muir was a Scottish-American naturalist and environmentalist, known for his profound love of nature and his efforts to preserve the wilderness in the United States. He played a crucial role in the establishment of national parks, including Yosemite National Park, and co-founded the Sierra Club, which advocates for environmental conservation. Muir's writings and activism inspired many to appreciate and protect the natural world. His passion for the outdoors led him to explore the beauty of the American landscape, and he is often referred to as the 'Father of the National Parks' for his dedication to preserving these natural treasures.