Amphitheater Mountain is an 11,042-foot peak in the Absaroka Range of northwestern Wyoming, near Yellowstone National Park’s Northeast Entrance and extending partly into the North Absaroka Wilderness. It rises sharply above Silver Gate, gaining more than 3,600 feet on its steep north side in only two miles. The mountain’s rugged character comes from the region’s volcanic history, shaped by material from early Eocene volcanoes about 50 to 55 million years ago that formed some of Yellowstone’s roughest terrain. In a subarctic climate, it endures long, cold, snowy winters, short cool-to-warm summers, and runoff that feeds tributaries of the Lamar River.