The very first national park, Yellowstone, was established in 1872. By 2013, the United States National Park Service was overseeing 4,000 parks, landmarks, seashores, and other protected areas. And the idea has gone global: Around the world, there are thousands of national parks protecting such gems as Africa's Serengeti and China's pandas.
"We save wild places so they might one day save us," writes Kim Heacox, author of The National Parks: An Illustrated History, a new book from National Geographic that looks back at the history of parks.
These photos from the book demonstrate the enduring power of preservation.