re: Random Google Maps browsing of the day.

In the early days of commercial aviation and air mail service, airplane pilots relied upon light beacons and enormous concrete arrows on the ground to find their way across the country. These navigation aids were built by the Department of Commerce in the 1920s and early 1930s to promote air travel.

Eventually more than 1500 beacons were erected. They were spaced about 10 to 20 miles apart along designated air routes.

The 1st picture is just outside of Albuquerque.