Found it!

My second search for the 41st mile marker of the NY-NJ border was successful!

My good friend Matt and I followed the old survey information walking 200 paces south from the now-nonexistent “Clark’s barn” to a site “between two roads” where after a short search we found the boundary marker.

This is not the original 1774 marker, which is lost to time, but the 1884 granite marker which survives well to this day. And clearly it is known to someone else, for it was marked with yellow paint along with the trees along the property boundary line. Interesting, the local land owners, hunters, and hikers I spoke to didn’t know of the marker, but they provided good information and conversation which led to the discovery.

Here are some pictures, marked “41,” “N Y,” and “N J.”