What’s more surprising: discovering the United States is dotted with giant concrete arrows — or learning the markers helped move the mail?
The Atlantic news site recently gave readers a bird’s eye view of the arrows, which were used in the 1920s and 1930s to guide the nation’s airmail pilots.
Approximately 1,500 arrows were built coast to coast, according to the Atlantic.
Pilots could peer out their cockpits and use the ground beacons to follow the Transcontinental Airway System. The arrows were next to rotating beacon lights that could be seen easily by day or by night.
By the 1940s, the arrows were already becoming obsolete. Many remain visible in barren stretches of Utah, Wyoming and Indiana, the Atlantic reports.
One state still uses the aviation aids: Montana, where pilots rely on about 19 arrows to fly through the mountains.
