The forgotten giant arrows

In 1924 these arrows were built ever 10 miles to assist planes in the airmail route across America
The concrete arrows can been seen from 10 miles in the air
This is an arrow built at the base of one of the few remaining beacon towers
Another arrow. You can find one on Google Maps here: 37°10'50.03"N 113°24'1.45"W
A model of what it looked like. There is the generator hut in the back, beacon tower, and arrow in the front of the tower
one of the few beacon towers saved
a saved generator hut
What the air mail route, with beacon locations, looked like from NY to SanFran.