I was recently going through some old USGS quadrangle maps my father owned that were printed in 1945.  I noticed that they still showed the locations of airway beacons across northeast Indiana.  We located one site in LaGrange County, IN where the old concrete arrow was still intact.  At another site, everything is gone but we did talk to the owner and he remembers the beacon well.  In fact, the rotating beacon from that site ended up at our local airport where it's still used today.