Graphic design from the skies in the 20's...and a bit of trivia.

Here's an example of graphic design from the 1920's.  Postal planes flew across the country from San Francisco to New York, but had no way of knowing where they were going.  Because of this, congress funded these giant 70ft long yellow painted arrows made of concrete. They were placed about 10-20 miles apart across the country, and each was accompanied by a 50ft tall tower equipped with a bright light to shine down on the arrow.  These could be seen from up to 40 miles away, and each arrow pointed to the next.  The towers are now gone because of the need of the steel in WWII, but the arrows remain, laid out across the midwest.