Preserved within Yellowstone are Old Faithful Geyser and some 10,000 hot springs and geysers, the majority of the planet's total. These geothermal wonders are evidence of one of the world's largest active volcanoes; its last eruption created a crater or caldera that spans almost half of the park.

The human history of the park dates back 12,000 years. The events of the last 130 years of park history are reflected in the historic structures and sites associated with various periods of park administration and visitor facilities development.