The Discovery of Yellowstone Park by Nathaniel Pitt Langford is the explorer's account of the Washburn Expedition of 1870, in which American explorers traveled through 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 Cook–Folsom–Peterson Expedition made the previous year.