Why is a huge concrete arrow pointing across the middle of the US?

There is no harbinger in America, a huge arrow lies on the ground, and there are things that are connected to the earth in some places rather than in one place. It is clearly hard to see as a traffic sign during driving,Landscape of NazcaLike "Who is for what?" It seems like I thought, but what is the meaning of a concrete arrow with a total length of 20 m?

What are These Giant Concrete Arrows Across the American Landscape? - Core 77
http://www.core77.com/blog/transportation/what_are_these_giant_concrete_arrows_across_the_american_landscape_25236.asp


The problem arrow is this. Such arrows exist from point to west of the Americas from the east to the west, but they are suddenly appearing on the isolated remote ground, and it is hard to see for road signs.


This involved the history of the United States and in the 1920s America the air mail service from the coast to the coast was started. However, the aerial map is still incomplete, so it is no wonder that the pilots lost their way because they did not purposely land on the land and asked the farmers "Where is this place?" It was nearly impossible to get to the destination when flying at night or in bad weather.


Introduced to solve this problem was a sign using a huge arrow, which was about 20m in size so that you can trace the way across the country even from the sky.


This arrow was colored with bright yellow and it was arranged in a set with about 15 m tower. At the top of the tower was installed a light powered by gas and a garage was also available at the foot.


Huge arrows were designed to be visible by 16 kilometers away from the place, with the next arrow about 5 km ahead depending on the direction of each arrow, so the pilots got to the destination without hesitation It has become possible to arrive at.

National Postal MuseumAccording to this tower is arranged at about 16 km intervals, the light lights are even about 60 km away from the placeI could confirmThere seems to be a statement that there is a possibility that the details may differ between the tower built early and the tower built in the latter half.

There are parts that are discussed separately, but it is clear that these towers are all past, the tower was dismantled, and the steel was consumed in World War II. However, unlike steel towers, the arrows remained in place without being used. The paint will peel off and it will be difficult to change it again to be worth it. Disassemble concrete which is no longer used and make it a material for new building constructionConcrete Recycling RobotsAs long as it is not sent, the arrow will continue to exist there forever.