Michael,
I first visited this tri-point June 21,1991. See attached picture of
Joyce Parsell and Clark Hall taken then. On Sept. 29, 2000 Joyce and
I were there again. Recently, after all of our discussions on this
point, I remembered a copy of a newspaper clipping which I got from
Mrs. Moreland, owner of the store across the road from the tri-point
when we were there in 2000. Sorry I didn't report on it sooner, but
I couln't find it until today. This article was from the Tulsa World,
Dec. 23,1998. Here are excerpts from the article:

The marker, a series of old landmarks that have been cobbled together
over more than a century, is, truth be told not much to look at.
Its top is made up of the first marker, a battered old rock with an
1820s inscription carved into its side.
It sits atop a larger concrete monument put in place by the Ozark
Culture Club in 1915. All of that resides in a concrete circle divided
into three parts, each located in a different State and each containing
its own little brass map identifying its location.

Mrs. Moreland also had another older article from the Joplin Globe, April
14, 1985 which she was unable to copy for me because of a problem with
her copier. Both articles mentioned this location as the westernmost
marker for the Mason-Dixon Line.
This article says that there is a marker in the center of the road with
asphalt over it.
Also says that the original location of the old stone was about 500 ft.
west, marked "MISR 1823", slightly over 1 ft. high. This stone was
constantly getting moved because it was in a wagon road. There were
other similar tales, so the conclusion was that no one knows where it
was originally.

I don't know whether we can believe these newspaper reporters, but it
does add a little fuel to the fire. Even the topo map doesn't help much.
See attachment for a 1:12000 NAD83 map of this area. Based on my
measurements the marker is about 31 ft. west of the center of the road.
Also it is 205 ft. south of the 36d 30'00" line and there is no mark
on the map at or near 319 ft. north of the present marker.

Your comments will be welcomed.
Jack