The Hayden Geological Survey of 1871 explored the region of northwestern Wyoming that later became Yellowstone National Park in 1872. It was led by geologist Ferdinand Vandeveer Hayden. The 1871 survey was not Hayden's first, but it was the first federally funded, geological survey to explore and further document features in the region soon to become Yellowstone National Park and played a prominent role in convincing the U.S. Congress to pass the legislation creating the park. In 1894, Nathaniel P. Langford, the first park superintendent and a member of the Washburn-Langford-Doane Expedition which explored the park in 1870, wrote this about the Hayden expedition: