LEFT: William Henry Jackson, Castle Geyser and Firehole Basin, 1871, courtesy Department of the Interior, National Park Service, Yellowstone National Park
RIGHT: Thomas Moran The Castle Geyser, Firehole Basin, 1872, Gilcrease Museum, Tulsa, Oklahoma
Soon after Moran returned east, Ferdinand Hayden and others (including executives of the Northern Pacific Railroad), began promoting the idea that Yellowstone should be protected and preserved as a national park. Because no member of Congress had seen Yellowstone, Hayden and his colleagues brought Moran's watercolors, along with the photographs taken by William Henry Jackson on the 1871 expedition, to Capitol Hill. Their images were later reported to have played a decisive role in the debate that led to the establishment of Yellowstone as the first national park in March 1872.