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Spread across the U.S. are a number of large concrete arrows. They are remanent of the early days of airmail. At the time pilots navigated by sight using landmarks to orient themselves. At night visual navigation was not practical. In order to facilitate nighttime flights a system of illuminated concrete arrows was implemented. From Sometimes Interesting's article Concrete Arrows and the U.S. Airmail Beacon System:
By 1924 the Postal Service developed a solution that was effective, if not elegant.
A system of ground-based navigation beacons extending from New York to San Francisco would help pilots fly across the country at night and ultimately be the world’s first such system.
The early iterations of the system used approximately 1,500 airmail beacons, each constructed roughly between 3 and 5 miles apart. The beacons featured a 50-foot tower with rotating lights placed on top of concrete foundations in the shape of giant arrows measuring between 50 and 70 feet long. To increase visibility of the concrete arrows, they were painted bright yellow.
Improvements to aerial navigation soon rendered the system obsolete and it fell into disrepair. There are still some of the concrete arrows existing, although they are often in remote locations and in bad shape.
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A restored beacon at the Grants-Milan airport Aviation Heritage Museum |
