Lost aviation navigation beacon and remaining concrete directional arrow.
On August 20, 1920, the United States opened its first coast-to-coast airmail delivery route, just 60 years after the Pony Express closed up shop.
There were no good aviation charts in those days, so pilots had to eyeball their way across the country using landmarks. This meant that flying in bad weather was difficult, and night flying was just about impossible.
The Postal Service solved the problem with the world's first ground-based civilian navigation system: a series of lighted beacons that would extend from New York to San Francisco. Every ten miles, pilots would pass a 70-foot concrete arrow on the ground which was painted a bright yellow. At the center of each arrow there would be a 51-foot steel tower and topped by a million-candlepower rotating beacon. 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. If needed, a generator shed at the tail (or feather end) of each arrow powered the beacon and lights.
By 1924, just a year after Congress funded it, the line of giant concrete markers stretched from Rock Springs, Wyoming to Cleveland, Ohio. The next summer, it reached all the way to New York and then extended all the way to San Francisco by 1929.
Around 1926, the new Aeronautics Branch in the Department of Commerce (or U.S. Postal Service?) proposed a 650-mile air mail route linking Los Angeles to Salt Lake City and passing through Washington County. It was designated as Contract Air Mail Route 4 (CAM-4). Western Air Express, Inc. was awarded a contract to lay out the route and carry the mail. Their first flight was made on April 17, 1926 in a Douglas M-2 airplane. By 1928, the route had been marked with the cement arrows and beacon towers for navigation at night and in inclement weather.
New advances in communication and navigation technology made the big arrows obsolete, and the Commerce Department decommissioned the beacons in the 1940s. The steel towers were torn down and went to the war effort. Today, only some of the weathered cement arrows (less the yellow paint) remain.