[foobarian]

We have some in northeastern US. However they don't necessarily sit on plot boundaries; I get the impression that surveyors put them wherever it is most convenient for them to better triangulate the land. We found one in our front lawn somewhere near the road, it was a small concrete square that turned out to be a pillar sunk deep into the ground.

[ghaff]

Not on my property in New England certainly. In fact, just went through an (expensive) process with a neighbor who wanted to get property lines squared away after they were botched on the initial property subdivision. We were fine with a handshake but both of us knew they really needed to be legalized with easements and such or any sale could become a nightmare.