Living In an era when airplanes can run on autopilot with no humans at helm, it is hard to imagine that there was once a time, not too long ago, when pilots in the USA had to navigate their way across cities using rudimentary aviation maps and . . . ginormous arrows!

In 1920, sixty years after the Pony Express, the horseback mail service that delivered messages, newspapers and even small packages shut down, the United States established the first bi-coastal airmail delivery system. However, given that good aviation maps were hard to come by, pilots often had to make their way to their destination by seeking out landmarks, which meant that flying at night or during bad weather, was almost impossible.

To overcome that the Postal Service came up with a brilliant idea - Creating a ground-based navigation system comprising of giant arrows that lit up all the way from New York to San Francisco. Made from concrete, they were painted a vivid yellow and surmounted by a 51-foot steel tower fitted with a brightly lit rotating beacon on top. The beacon was powered by a generator that was attached to the tail of the arrow.

Placed ten miles apart, these arrows allowed the pilots to make their way across the country easily - This simple but ingenious idea revolutionized the postal service! Now, instead of waiting for weeks, people could get their mail delivered to them in 30 hours or less. It worked so well that by 1924, a year after it was funded by Congress, the giant arrows began to appear all over the continent - from Rock Springs, Wyoming to Cleveland, Ohio, making the United States Postal Service a source of envy for mail delivery systems all over the world.

Of course thanks to advances in navigation technology and communications, what seemed like a brilliant idea in the 1920's did not seem as great just two decades later. By the 1940's these giant beacons of light were decommissioned and shortly after, the steel towers were torn down and the material recycled for use in the second World War efforts.

The only remnant of this brilliant flight navigation system? The huge arrows that dot the landscape of the country till this day. While their shiny paint is gone and their concrete is a little beaten up, they remain as majestic as they were, over 90 years ago - So be sure to look out for them the next time you are on a hike or in the countryside. If you are one of those lucky people that have already encountered them, be sure to let us know, by adding your comments below.