at last an example has been found of the elusive earthen 
mounds erected in 1799 by andrew ellicott as mile markers from 
the mississippi to the chattahoochee river along the 31st parallel 
as well as from the apalachicola to the st marys river on the 
present flga state line 
to mark the boundary between spain & the usa that existed there 
between 1795 & 1819
http://www.aspls.org/history/mound.html
at the same site 
a pic of the only stone marker left on that line by ellicott
which still serves today to mark the initial point of a major 
meridian in the public land system
http://www.aspls.org
& some more background info on the mounds & the stone
http://www.aspls.org/history
this little rock btw is the monument mentioned but not pictured in 
message 6526
which you may recall was a first try at rounding up all the former 
international boundary monuments still standing within the 
united states
& where there is a link to the picture of the other much taller rock
a relic on modern latx of the boundary that existed there between 
the republic of texas & the usa between 1835 & 1845
but now that an ellicott mound has been found
it is clear that such marks are just as monumental as the rocks
so the claim made in that message that there are only 2 extant 
members of this rare class must be enlarged to include an 
unknown number of the surviving mounds