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In 1920, the United States opened its first coast-to-coast airmail delivery route. Before radio navigation was common in airplanes, pilots had to navigate by landmarks. Therefore, bad weather and nighttime essentially grounded the airplanes. The solution was to build a system of concrete arrows — stretching 70 feet along the ground — every ten miles from New York to San Francisco. Each arrow had at its center a steel tower with a beacon on top. 

When I first saw this picture, I asked myself, “Why is an arrow made of concrete doing in the middle of nowhere?” The caption to the photo provides the answer. Sometimes I wish had signs large pointing in which direction to go in life. It also made me see how far technology has taken us in 96 years!