[TexanToTheCore]

The stone was probably ballast for a shallow draft boat. The width of it my be the width of the boat used.

[crystalk]

So maybe they even had stones cut to this size and shape, to fit the boat hull...I wonder if anyone has ever analyzed the stone to see if it might be from Europe, Greenland, or Iceland...but it was always said to be not from the local outcropping on the hill (now called Runestone Hill) where it was found...