"Old Faithful" geyser erupts in Yellowstone National Park's Upper Geyser Basin in the western U.S. state of Wyoming. Old Faithful was named in 1870 during the Washburn-Langford-Doane surveying expedition, during which the explorers sometimes washed their laundry between eruptions of the hot spring! The first geyser in the park to receive a name, Old Faithful is one of the most predictable geographical features on Earth, erupting every 35 to 120 minutes. Photo by Carol Highsmith, 2016.