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<ul><li><b>Scope and content:</b>  Photograph from Volume Two of a series of photo albums documenting the construction of Hoover Dam, Boulder City, Nevada.  Full caption of photograph reads:</li></ul>
"View looking into Black Canyon from rim of the Arizona wall showing operations in the early stages of the upper cofferdam construction. Temporary cofferdam diverts river flow through Arizona side of channel. Nevada side inside temporary cofferdam is partially unwatered and muck is being removed by dragline, shovel, and truck. Upstream slope of cofferdam proper is indicated by white paint line on Nevada wall above truck road. Temporary barrier will be dumped from bridge near which pile driver barge is anchored, and will divert entire river flow through Diversion Tunnels Nos. 2, 3 and 4 during cofferdam construction. First diversion will be through Tunnel No. 4 during the latter week of October."</div>
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Unknown author<span style="display: none;">Unknown author</span> or not provided</div>
<a href="https://en.wikipedia.org/wiki/U.S._National_Archives_and_Records_Administration" class="extiw" title="en:U.S. National Archives and Records Administration">U.S. National Archives and Records Administration</a>