On top of a small hill within the city limits of Montague, California is the remains of this aviation arrow.  Before our current GPS satellite & radar, airplane pilots who did transcontinental airmail routes at night would fly following these large cement arrows built high up on ridges or mountaintops, often accompanied by beacons with a light.  While there were over 1500 of them across the country back in the day, about 100 of them remain today, decaying & forgotten like this one.  This one was the 28th arrow of the San Diego - Seattle airway route which was officiated in September 1926 & lasted for a few years until radar came.  Pilots would follow the beacons & directions of the arrows using a compass to stay aligned w/ each arrow until they encountered the next one, directing them ultimately to Seattle.  This particular arrow points directly in the direction of Black Butte no more than ten miles north where the next cement arrow still exists today, though access to that one is on private land.  There is another arrow just south of here near Gazelle which points to this one in Montague.  Most of these sites are now gone, particularly during WWII as a means of making sure any enemy aircraft didn't use these features to scout out American soil.