We have become so accustomed to modern avionics that we almost forget how wondrous GPS actually is, and perhaps even take it for granted. Talk to an old timer and he may tell you how impressed he was with LORAN when it came out. Of course the older guys will regale you with stories about VOR and NDB approaches and navigation.
But there are probably few people alive today that can talk about flying without radios at all. About 100 years or so ago, the US Department of Commerce established federal air routes, where pilots would look for large concrete arrows on the ground. These arrows were up to 70 feet long, usually painted yellow, and placed 10 to 15 miles apart. At 3000 feet, pilots could usually see from one to the other. Beacons were installed for night flight.
The purpose was to move the mail. Remember the airmail postage stamp? The United States Post Office Department issued the first airmail stamp in 1918 and it was a big deal to get mail bearing that stamp.
Where were they placed? Basically, all over the United States. You could fly from New York to San Francisco, simply following these large arrows. But then came the electronic age, and by the 1940s, the system was replaced by navigational radio systems. During World War II, numerous concrete arrows were destroyed as well – so as to not help enemy pilots visually navigate the country. The cool thing is, even though the system has it been out of use for over 70 years, you still find remnants all over the country, including here in South Carolina.
A visible arrow from Beacon 14, originally of the Atlanta–New York line, can be seen near Woodruff, SC. The arrow is also clearly visible in Google Street view, and, while slightly overgrown by vegetation, you can still see a concrete pad near Effingham.