Remonumenting A Meridian Stone in Benchmarking Posted June 30, 2005 My understanding is that borders, such as the NM-CO border, are set by the monuments, and not by an arbitrarily measured lognitude line. As such, the Mason-Dixon stones being recovered recently by one of our own might be very important to establishing the PA-WV-MA border. Any word on that? That is partially true. Some state borders were intended to be along a certain (not necessarily arbitrary) line of latitude or longitude. The discrepancy happens because the original surveyor did not get exactly on the line he was supposed to. You a correct that the monuments themselves become very important because they mark where the line was established on the ground.