Portal of the abandoned tunnel of the Alleghany Portage Railroad near Johnstown, Pennsylvania, the first railroad tunnel in the United States
Unknown photographer
Hungerford, Edward, <i><a rel="nofollow" class="external text" href="http://www.gutenberg.org/files/40242/40242-h/40242-h.htm">The Modern Railroad</a></i> (Chicago: A.C. McClurg &amp; Co., 1911), p. 155.