Had a talk with the maps person at the courthouse close to 10 years ago, they redrew some county map lines based on existing deeds. My map line on one side shifted just slightly, but still shows I go over a good ways past what was an interior fence when I bought the place.
I walked the line using Landglide, there is a climber in a tree that is right smack dab on my line. That climber was put there sometime during the season last year, I found it late in the season. No one has been back to it since I found it. I think they poached the 11 point I was after early last year, lucky for them that I didn't find that stand while they were in it.
Also using Landglide I have used the measure tool looking at the deed of the neighboring property to confirm my point at the road matches the map almost exactly, within maybe a yard. When the property on that side of me changed hands I measured that same line with my rangefinder and it also came to the same point. Being that onx uses the tax maps, I think for our property should be close.