From this vantage point, the view stretches from the Aquarius Plateau along the northern horizon to Navajo Mountain on the Utah-Arizona border, encompassing the maze of deep, winding canyons that form the Escalante River basin. In 1872, during the second Powell Expedition, Almon H. Thompson wrote that no animal without wings could cross the deep gulches in the sandstone basin below, and that the stream they had followed was an unknown, unnamed river draining the eastern slope of the Aquarius Plateau through a deep, narrow canyon to the Colorado River; believing themselves its discoverers, the party decided to name it the Escalante River in honor of Father Escalante and to call the country it drains Escalante Basin. The Henry Mountains were the last mountain range in the continental U.S. to be mapped and named because of their rugged remoteness, and they are home to one of the few free-roaming bison herds in the country, introduced there in 1941. Navajo Mountain, known to the Navajo people as Naatsis’áán, or “Head of the Earth,” stands on the Utah-Arizona border south of the Colorado River, and water flowing from this 10,416-foot laccolith dome carved a labyrinth of sandstone formations, including Rainbow Bridge, the world’s largest natural bridge.