From an article about modern day Greer descendants visiting in Dumfriesshire:More details about the Griersons of Lag can be found in The Scottish Nation..... :
.. a descendant of James Grear who immigrated to Gun Powder River, Maryland in 1674, before it was the United States. He was the son of Sir James Grier(son) (c1604-1666) and Mary Browne and he was born about 1604 in Capenoch, Dumfrieshire. [Note: They are my ancestors, too]
Mr. Crawford’s tour started at the ancient Lag Tower ruins, the first home of the Griersons and the ancient seat of the Grierson clan. Lag Castle is situated on a knoll adjacent to a farmstead, beside Lagg farm, midway between Dunscore and Glenmidge in Nithsdale.
At Facebook: Grierson & McGregor Are Synonymous (maybe, maybe not).