Opposite the head of this arm [South Arm of Yellowstone Lake] is the great yellow mountain seen from Mount Langford several days ago. This is the central point from which radiate double barriers, separating the waters of the Yellowstone from the Snake, and the latter from the Madison, Snake River flowing on the east side of the mountain southerly, and the Firehole branch of the Madison rising in a small lake to the west of the range, the main branch coming from Henry's Lake, south of this. This mountain may be said to be the focus of volcanic action in the basin, the greatest phenomena being observed within a radius of thirty miles from its summit. From its yellow, sulphureted appearance it can be readily distinguished, and is the central and most important landmark in the great basin.
The summit can be reached via the Mount Sheridan Trail 3.3 miles (5.3 km) which spurs off the Heart Lake Trail at the northwest corner of Heart Lake. This is steep climb of 2,700 feet (820 m) in 3 miles (4.8 km), but provide extraordinary views of the park in all directions to include the Grand Tetons to the southwest.