The End of the Known world is the author's name for a limestone escarpment in Wyoming's Big Horn Mountains. Its location remains unnamed on any map. Over a period of twenty years, its physical and spiritual power has lured her many times to travel on foot to this precipice. As she hikes this time, however, new questions arise: What is it about certain places that calls to us? Do they sometimes wish we would leave them alone? What is the meaning of sacred space? On this journey, the author, now in her sixties, poses these questions to the genius loci, the Greek term for the particular spirit that inhabits sacred locations here on earth. As she hikes over difficult terrain, the author confronts some unexpected physical changes, such as a lack of balance when moving down a steep incline. These bodily changes parallel environmental changes, such as bark beetle damage to many Douglas fir trees that, on her first visit, stood tall and strong at the End of the Known World. The completion of her journey, however, reveals important discoveries. Mollusk fossils inscribed into limestone remain as evidence that the ground on which she stands was once an ancient sea. Eastward, over the Big Horn Basin, soft stripes of gray, blue, and white obscure the horizon, where Mother Earth marries Father Sky. The voice of the genius loci speaks of the love between person and place, and of the impermanence of all things.