The Washburn Expedition of 1870 explored the region of northwestern Wyoming that two years later became Yellowstone National Park. Led by Henry D. Washburn and Nathaniel P. Langford, and with a U.S. Army escort headed by Lt. Gustavus C. Doane, the expedition followed the general course of the CookFolsomPeterson Expedition made the previous year.During their explorations, members of the party made detailed maps and observations of the Yellowstone region, exploring numerous lakes, climbing several mountains, and observing wildlife. The expedition visited both the Upper and Lower Geyser Basins, and after observing the regularity of eruptions of one geyser, decided to name it Old Faithful, since it erupted about once every 74 minutes.

One member of the expedition, Montana writer and lawyer Cornelius Hedges, later wrote a number of articles for a Helena, Montana-based newspaper, describing the things the expedition had witnessed. In discussions with other members of the party and in his writing for the newspaper, Hedges was a vocal supporter of setting aside the Yellowstone region as a National Park, an idea originally proposed by former acting Montana Territorial Governor Thomas Francis Meagher.

Old Faithful is a cone geyser in Yellowstone National Park in Wyoming, United States. It was named in 1870 during the Washburn–Langford–Doane Expedition and was the first geyser in the park to be named. It is a highly predictable geothermal feature and has erupted every 44 minutes to two hours since 2000. The geyser and the nearby Old Faithful Inn are part of the Old Faithful Historic District.