“The Yosemite Falls and Valley, California.” Page 10. Engraved and printed by Illman Brothers, Philadelphia. Collection of the Library of Congress. Sloan Foundation, digitalizing sponsor. In the public domain. via https://archive.org/details/greatwestitsattr00brod/page/n9
“Winter Forest Scene in the Sierra Nevadas.” Thomas Moran, artist. Page 86. Collection of the Library of Congress. Sloan Foundation, digitalizing sponsor. In the public domain. via https://archive.org/details/greatwestitsattr00brod/page/n85
“The great blue spring of the Lower geyser basin, Yellowstone.” ca. 1875. Chromolithograph published by L. Prang and Company. Collection of the Library of Congress http://www.LOC.gov ID 94515827. In the public domain due to age. via https://www.loc.gov/item/94515827/
“Yellowstone Lake.” ca. 1875. Chromolithgraph. L. Prang and Company, Lithographer. Collection of the Library of Congress http://www.LOC.gov IDpga.12036. In the public domain due to age. via https://www.loc.gov/resource/pga.12036/
“Castle Geyser, Yellowstone.” 1874. Chromolithograph by L. Prang and Company. Collection of the Beinecke Library, Yale University, New Haven. Artwork in the public domain in the United States because the artist has been dead over 70 years. via https://en.wikipedia.org/wiki/File:Castle_Geyser,_Yellowstone,_1874.jpg