As the flagship U.S. National Park, Yellowstone,throughout its administrative history, has set many precedents for park management policies and practices across the United States. This essay examines the period of administration of the park by the United States Army from 1886 to 1916, which was especially formative for Yellowstone. The army reversed the trend of ineffective leadership in administering the park. The policies enacted during that period — regarding nature, wildlife, and tourism management — laid the groundwork for the administration of Yellowstone. In turn, many of these best practices were adopted by subsequent national parks. Most importantly, the army's work served as a major factor in the very preservationof the national parks system. Therefore, the park administration by the United States Army left a lasting legacy that is still evident in both Yellowstone and many other national parks today.