Concrete Arrows and the U.S Airmail Beacon System.

Scattered across the United States are a network of mysterious concrete arrows. They are often found in remote locations or areas difficult to access. Some will be accompanied by a small shack, a few have a metal tower affixed to their base. Many are in good condition while others have succumbed to nature. The shape and direction of the arrows vary, but it is clear they served the same purpose.

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