Camp Century trench construction in 1960.  <a href="https://en.wikipedia.org/wiki/Project_Iceworm" class="extiw" title="en:Project Iceworm">Camp Century</a>
U.S. Army Corps of Engineers, Cold Regions Research and Engineering Laboratory
1960
<p>Camp Century Evolution of Concept and History of Design Construction and Performance, Technical report 174 (<a rel="nofollow" class="external text" href="http://www.dtic.mil/dtic/tr/fulltext/u2/477706.pdf">PDF</a>), fig. 14, p. 15
Publication Date 1965
</p>
Photo taken in 1960