Old Faithful in Yellowstone National Park, Wyoming. Photo by mark byzewski

Old Faithful is a cone geyser located in Wyoming, in Yellowstone National Park in the United States. Old Faithful was named in 1870 during the Washburn-Langford-Doane Expedition and was the first geyser in the park to receive a name. It is also called the most predictable geographical feature on Earth erupting almost every 91 minutes. The geyser, as well as the nearby Old Faithful Inn, is part of the Old Faithful Historic District.