Concrete arrows: Relics of early US Air mail navigation
In the USA, enormous overgrown concrete arrows can still be found, serving as relics of an early navigation system. These large symbols, visible from great heights, are remnants of an old infrastructure that can be considered a precursor to today's GPS.
9:09 AM EST, November 25, 2024
These concrete arrows were part of a bold project from the beginning of aviation. The pioneering task of airplanes was to transport mail. However, as this task developed, a challenge arose: How can we navigate effectively to reach the destination precisely? In areas with diverse landscapes, distinctive points could be used as indicators. The problem arose on vast plains where pilots primarily had to rely on the sun. Navigating by stars was also difficult at night when the sky was overcast.
Transcontinental Airway System – how was navigation formed?
The solution to these problems was the ingenious Transcontinental Airway System, which served as the postal infrastructure on a large scale.
Starting in 1923, markers were constructed—large, several dozen-foot concrete arrows covered with bright yellow paint, visible from a great distance, even from an altitude of 10 miles. At the top of each arrow, a concrete platform was installed with a 53-foot lattice navigation tower, which, like a lighthouse, was equipped with a 24-inch spotlight activated at night.
Additionally, each installation had colored lights emitting Morse code signals with an identifier, and in areas without power lines, small houses were built with power generators.
Within a year, arrows placed every several miles outlined a route connecting New York and San Francisco, covering nearly 2,700 miles and utilizing 284 markers.
The concrete navigation system proved effective—previously, mail was transported by cars at night, but with the Transcontinental Airway System, flights became possible around the clock. The infrastructure included emergency, lit-at-night runways every several dozen miles.
Concrete arrows on the continent - what are they used for?
Thanks to the Transcontinental Airway System, delivering a letter across the USA took only two days. The system quickly expanded to 1,500 arrows outlining a network of 18,000 miles of airways.
Soon, however, modern technologies such as radio navigation began to replace this infrastructure. During World War II, some installations were dismantled to avoid aiding navigation for enemy air forces.
Many concrete arrows still survive today. To find them, simply use Google Maps. Currently, 14 active markers still function in Montana.
