When the Feds Took Away Our Arrows

In some of the wild parts of America, usually in a desert, you might be hiking along and come across a large but deteriorating concrete arrow on the ground, maybe 70 feet long, in the middle of nowhere. If you follow the arrows, they will lead you to San Francisco.

In 1920 these arrows ran from New York to the west coast, one arrow every ten miles. Of course many of them are gone now. Question: Who made them and why?

The arrows were built by the federal government to guide early airplanes carrying the mail. They were decommissioned in 1940.