Hayden’s survey team consisted of approximately three dozen men, including several scientists. They later split into smaller groups to explore more territory. The Hayden Survey en route, 1871. National Archives, Records of the U.S. Geological Survey

Hayden reported, “Standing near the margin of the Lower Falls, and looking down the Cañon . . . with its sides 1,200 to 1,500 feet high, decorated with the most brilliant colors that the human eye ever saw, the rocks weathered into an almost unlimited variety of forms.” Lower Falls of the Yellowstone, 1872. National Archives, Records of the U.S. Geological Survey