A much better writeup is here: <a href="http://sometimes-interesting.com/2013/12/04/concrete-arrows-and-the-u-s-airmail-beacon-system/" rel="nofollow">http://sometimes-interesting.com/2013/12/04/concrete-arrows-...</a>
>A generator shed at the tail of each arrow powered the beacon<p>And who were the poor souls that had to drive up to these generators and fill them with diesel every so often? These things couldn't have been off major roads so I imagine this meant a lot of off-road driving. Considering this spanned the nation, the number of staff involved in just keeping the lights on must have been significant.<p>The article is probably wrong about this replacing the Pony Express. By the 1920s long distance mail was sent via train. I can't imagine the post office still using horses for long hauls.<p>Wikipedia has more info:<p><a href="https://en.wikipedia.org/wiki/Transcontinental_Airway_System" rel="nofollow">https://en.wikipedia.org/wiki/Transcontinental_Airway_System</a><p>>The beacons flashed identification numbers in Morse code. The sequence was "WUVHRKDBGM" prompting the training phrase "When Undertaking Very Hard Routes Keep Directions By Good Methods." to remember the sequence<p>I find this part fascinating. More info here:<p><a href="http://everything2.com/title/WUVHRKDBGM" rel="nofollow">http://everything2.com/title/WUVHRKDBGM</a>
Relatedly (and including this article in the comments), there was a submission yesterday about the giant X's in the desert[1].<p>1: <a href="https://news.ycombinator.com/item?id=12695179" rel="nofollow">https://news.ycombinator.com/item?id=12695179</a>