According to the journals kept by members of the expedition, Old Faithful was discovered around September 18, 1870. Although Yellowstone is home to around 500 geysers, Old Faithful is unique because eruptions are very predictable. Because of this, Old Faithful has become known as the largest consistent geyser, and is a popular tourist destination.
Nathaniel P. Langford, member of the Washburn-Doane Expedition wrote about seeing his first geyser, Old Faithful, as follows:
Judge, then, what must have been our astonishment, as we entered the basin at mid-afternoon of our second day's travel, to see in the clear sunlight, at no great distance, an immense volume of clear, sparkling water projected into the air to the height of one hundred and twenty-five feet. Geysers! geysers! exclaimed one of our company, and, spurring our jaded horses, we soon gathered around this wonderful phenomenon. It was indeed a perfect geyser. The aperture through which the jet was projected was an irregular oval, three feet by seven in diameter. The margin of sinter was curiously piled up, and the exterior crust was filled with little hollows full of water, in which were small globules of sediment, some having gathered around bits of wood and other nuclei. This geyser is elevated thirty feet above the level of the surrounding plain, and the crater rises five or six feet above the mound. It spouted at regular intervals nine times during our stay, the columnns of boiling water being thrown from ninety to one hundred and twenty-five feet at each discharge, which lasted from fifteen to twenty minutes. We gave it the name of Old Faithful.