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.
The purpose was important: helping early pilots navigate U.S. transcontinental flights at night.
In a era before radar, pilots used ground-based landmarks for guidance. This solution worked for flight during the day, but grounded pilots at night. Before long, a system of beacons was established across the United States to guide airmail pilots around-the-clock. When radar and radio communications made the beacons obsolete years later, most were torn down or abandoned.