September 18, 1870 – Old Faithful Geyser is observed and named by Henry D. Washburn during the Washburn-Langford-Doane Expedition to Yellowstone.
Old Faithful is a cone geyser located in Yellowstone National Park in Wyoming, United States. Old Faithful was the first geyser in the park to receive a name an it is one of the most predictable geothermal features on Earth. Since 2000, it has erupted every 44 to 125 minutes.
Eruptions can shoot 3,700 to 8,400 US gallons (14,000 to 32,000 L) of boiling water to a height of 106 to 185 feet (32 to 56 m) lasting from 1.5 to 5 minutes. The average height of an eruption is 145 feet (44 m). Intervals between eruptions can range from 35 to 120 minutes, averaging 66.5 minutes in 1939, slowly increasing to an average of 90 minutes apart today. (from Wikipedia)
The U.S. Postal Service has issued 3 stamps featuring the geyser. The first was a 5-cent stamp commemorating Yellowstone National Park on July 30, 1934 as part of the National Parks series (Scott No. 744). In imperforate variety of this stamp was also printed (Scott No. 760). The second is an 8-cent stamp issued as a part of the 1972 National Parks Centennial series (Scott No. 1453). The most recent issue is a $17.50 Express Mail stamp which pictures the geyser and a buffalo in the foreground (Scott No. 4379).