Though providing spectacular features that bemused and befuddled the park's earliest visitors, the volcano is known to have been been the largest to have ever occurred on Earth, resulting in the worldwide population falling to as little as 10,000 people.

The park was named for the yellow rocks seen in the rock cliffs along the northern portion of the Yellowstone River. The iron in the rocks casts causes them to cast a yellow tint that the Native Americans first called "Mitzi-a-dazi," or the "River of Yellow Rocks." Later French fur trappers translated this to "Yellow Rock" or "Yellow Stone."

Gathered from archeological evidence, Native American history is said to date back as far as 12,000 years. These earliest people were known to have been primarily hunter-gathers who utilized significant amounts of obsidian to make cutting tools and weapons. They may also have practiced some crude farming activities. Arrowheads made of Yellowstone obsidian have been found as far away as the Mississippi Valley indicating that a regular obsidian trade existed between Yellowstone Native Americans and tribes further east.

In 1806, when the Lewis and Clark Expedition moved through the area, a man named John Colter left the expedition, joining a group of fur trappers. Colter is credited as being the first non-Native American to visit the region and make contact with the Indians. These Native Americans, referred to as Sheepeaters, were a band of Shoshone, who  survived by hunting for bighorn sheep and fishing the headwaters of the Snake, Madison, and Yellowstone Rivers.

Colter spent the winter of 1807-08 traveling, trapping, and exploring Yellowstone, before moving down into what would be known as Jackson Hole, and crossing the Grand Tetons into Idaho. However, his adventure ended when in the fall of 1808, he was captured by Blackfoot Indians. Stripped naked, Colter was somehow able to escape. When he returned to Missouri from his adventures, people mocked his stories of steam rising from the earth and boiling mud as mad hallucinations, earning Yellowstone its first name as "Colter's Hell".

In 1857, mountain man, Jim Bridger led an expedition to Yellowstone. He also returned with stories of boiling springs and spouting water; however, because he had already earned a reputation of one to tell "tall tales," his accounts were largely ignored.

Tall tales or no, the stories of told by Colter and Bridger aroused the interest of the interest of explorer and geologist Dr. Ferdinand V. Hayden. In 1859, Hayden began a survey of the upper Missouri River region, accompanied by U.S. Army surveyor W.F. Raynolds and Jim Bridger acting as a guide.

Unfortunately, the party was unable to reach Yellowstone region due to heavy snows. Afterwards, the Civil War stopped all attempts to further explore the region and Hayden would not be able to fulfill his mission to explore the area for another eleven years.

Before Hayden could return another expedition was organized by a group of Montanans in 1870. Referred to as the Washburn-Langford-Doane Expedition, the group was led by the surveyor-general of Montana Henry Washburn. Also part of the group was a man named Nathaniel P. Langford, who would later become known as "National Park Langford" and the first superintendent of Yellowstone Park. Spending about a month exploring the region, the expedition named many of the sites of interest, that continue to be used today.

In the meantime Dr. Hayden had been working with the government to sponsor a second expedition to Yellowstone and discussions were already in progress to make Yellowstone a National Park. In early 1871, the U.S. Geological Survey sponsored Hayden's second trip to the park. Along with Hayden were naturalists, geologists, a landscape artist, and two photographers.