John K. Hillers 1873 Tower walls [U.S. topographical and geological survey of the valley of the Colorado River of the west, by J.W. Powell and A.H. Thompson. No. 026]
Stereoview Library of Congress, Prints and Photographs Division Reproduction Number: LC-DIG-stereo-1s00785 (digital file from original photo, front) LC-DIG-stereo-2s00785 (digital file from original photo, back)
