U.S Airmail Beacon System - Arrows and Beacons

Spread across USA there are giant concrete arrows. These arrows were used for directing airmail planes in early 1900s to 1930s. As most of the routes would be too dangerous during the night/bad weather and the pilots sometimes forgot where the different routes went. These giant concrete arrows were created and also had a beacon beside them that would have a bright flashing light to help guide air mail planes during the night. Most of the arrows are quite hard to see on Google Earth, but I have gathered links with pictures. Today most of them are still there, but are overgrown or on private properties.