Depths shown by gradient tints. "*GPO: 1996--404-952/40020. Reprint 1996." Includes text and ill. Text and ill. (some col.) on verso. Available also through the Library of Congress Web site as a raster image.
United States. National Park Service
<a rel="nofollow" class="external free" href="https://www.loc.gov/item/96683863/">https://www.loc.gov/item/96683863/</a>