From sometimes-interesting.com: "Scattered across the United States are a network of mysterious concrete arrows. They are often found in remote locations or areas difficult to access. Some will be accompanied by a small shack, a few have a metal tower affixed to their base. Many are in good condition while others have succumbed to nature. The shape and direction of the arrows vary, but it is clear they served the same purpose.
The purpose was important: helping early pilots navigate U.S. transcontinental flights at night."
There are a few of these crumbling arrows left in the El Paso area, but most are on private property. Here is one right off of highway; you've probably passed it numerous times on the way to Carlsbad Caverns.