In my area (the southwest), it's not unusual for modern municipal airports to have their standard airport beacon mounted on a tower that was originally installe

In my area (the southwest), it's not unusual for modern municipal airports to have their standard airport beacon mounted on a tower that was originally installed for an airmail route beacon. Sometimes the tower has been moved, but sometimes it sits on the original base, usually sans arrow as it seems that intermediate fields (which were often later turned into municipal airports) didn't always have an arrow installed. My old home of Socorro, N.M. has such an example, and although I have not been able to properly confirm this it appears that the airport beacon there is actually the original airmail route beacon with lenses and electrics replaced. It nicely matches the drawings I've seen of the beacon lights. Many, even most, of the municipal airports in the southwest date back to CAA intermediary fields often placed along beaconed air routes, so keep an eye out in AZ, NM, TX. I'd guess this is true of other fairly rural states as well. In Grants, N.M. there is a particularly interesting example at the municipal airport. There, there's a fully intact and nicely painted generator hut and beacon tower. It's been restored and is now operated by a historic society. Unfortunately, it had to be moved from its original location on a nearby hilltop into town because the actual beacon once located at the present site of Grants airport was removed many years ago. Still, one of very few I know of that is being preserved as a museum piece. To my knowledge the arrows were not lit. In many places there are beacons without arrows, my understanding is that this was done because, at night, the next beacon was supposed to be visible by the time you flew over the previous beacon so that you knew which direction to head. During the day the arrows could be placed less frequently, generally only at turns, since pilots could see the direction and the towers in between would serve as confidence markers that they were on course.