Grand Prismatic Spring

The Grand Prismatic Spring in Yellowstone National Park is the largest hot spring in the United States, and the third largest in the world, next to those in New Zealand. It is located in the Midway Geyser Basin.

The first records of the spring are from early European explorers and surveyors. In 1839, a group of fur trappers from the American Fur Company crossed the Midway Geyser Basin and made note of a “boiling lake”, most likely the Grand Prismatic Spring, with a diameter of 300 feet (91 m). In 1870 the Washburn-Langford-Doane Expedition visited the spring, noting a 50-foot (15-meter) geyser nearby (later named Excelsior).