During the late 1920s and early 1930s, the US Department of Commerce created an air mail route between Los Angeles and Salt Lake City. These enormous arrows helped pilots stay on course. The historical society of Washington County, Utah explains:
Large concrete arrows were constructed on the ground along the way as visual navigational aids for the planes flying the mail route. There were built at intervals of approximately 10 miles and were about 70 feet long. Typically, there was a 51-foot beacon tower in the middle of the arrow topped with a powerful rotating beacon light. Below the rotating light were two course lights pointing forward and backward along the arrow. The course lights flashed a code to identify the beacon's number. A generator shed, where required, stood at the "feather" end of the arrow.
(Photo: Washington County Historical Society)