Final answer:
John Muir is known as the father of national parks for his influential advocacy and conservation efforts.
Step-by-step explanation:
The father of national parks is John Muir. He was an environmentalist and the founder of the Sierra Club. John Muir played a crucial role in advocating for the preservation of natural areas, including California's Sierra Nevada Mountains and Yellowstone National Park. His efforts in documenting the importance of preserving these landscapes and his influence on policy initiatives led to the establishment of the national park system in the United States.