Final answer:
John Muir, the early twentieth-century conservationist who founded the Sierra Club, is known for advocating the preservation of California's Sierra Nevada Mountains and influencing national conservation policy.
Step-by-step explanation:
The Californian ecocentrist and anthropocentrist who argued for the protection of America's natural environment in its pristine, unaltered state was John Muir. He was a leading conservationist of the early twentieth century, who founded the Sierra Club and was instrumental in documenting the importance of preserving California's Sierra Nevada Mountains.
His advocacy for the preservation of wild places sprang not only from their inherent beauty and utility but also from the belief in their spiritual and restorative power as per transcendentalist philosophy. Muir's influence extended to inspiring President Theodore Roosevelt to set aside millions of acres for forest reserves and helped establish the foundation for the national park system.