Along the border of Montana and Wyoming lives a herd of wild horses unlike any other in North America. Theirs is a world that towers above the surrounding landscape high amongst the clouds. Known as the Pryor Mountains, the geology here makes up what's known as an island in the sky. The horses themselves trace their ancestry back to the Lewis and Clark expedition, when Seargent Pryor was tasked with transporting the Corps of Discovery's horses back to Fort Manden after their successful return to