Terry Tempest Williams is the author of 15 books. This essay is excerpted from The Hour of Land: A Personal Topography of America's National Parks, published by Sarah Crichton Books/Farrar, Straus and Giroux (2016).

Ian Shive is an award-winning outdoor photographer. His latest book, The National Parks: An American Legacy (Earth Aware Editions, 2016), includes 200 unique photos of our country's parks. See more images from the book.