EARLY AVIATION NAVIGATION ARROWS
How do you think that early pilots knew where they were going when they didn't have radar or sophisticated maps? It was news to me when I found out about this: Aviation navigation arrows... Thirty foot concrete arrows placed ten miles apart in Southern Utah to help the early airmen get to where they were going safely. During the day, the pilots would simply look down, see the arrow, and follow it to the next one. By night, the arrows were lit by gas lanterns.
With progress and more sophisticated methods, the concrete arrows fell out of use by the early 1930's. Today, only a few of the markers remain. Mostly forgotten, crumbling into nothing.