FOR MOST OF August 1883 a military expedition headed by President Chester A. Arthur and guided by Lt. Gen. Philip Sheridan crossed 500 miles of lightly settled Wyoming Territory. The goal was to reach Yellowstone National Park and tour it before returning to civilization. Arthur was the first president to visit the park, and the only president to make an extensive overland march, mostly on horseback. A primary objective of the expedition was to raise the awareness of U.S. citizens to the attractions along the route, and the need for preservation of the park, which was threatened by vandalism, commercial development, and official neglect.