Don,
Thank you so much for responding - especially so quickly. I am a teacher, so I am a bit crazy here at the end of the school year.
I do believe you are correct about the Fourth Duke; I think he would have been the one who "raised her" during her formidable years. I have researched his siblings and his children and no one seemed to have had a daughter named Catherine. It is so weird! Apparently, the story goes that she and William were both born in Scotland and only moved to the states after they married.
The following is an excerpt from History of North Carolina Volume VI:
William Williamson, the father of Isabella, had an interesting and adventurous career. He was a man of fine education, his home being in Glasgow, Scotland. Before leaving his native country, he engaged in teaching English, Latin, and Mathematics, first in private families and later in colleges, but when he had won the love of Catherine Campbell, the niece and adopted daughter of the Duke of Argyle, to the extent that she was willing to go with him to the ends of the earth and the proposed match proving unsatisfactory to the Duke on the ground that Williamson was only a teacher and not the owner of an estate, the married couple sailed for America and landed on the Island of Jamaica, where they remained for two years and afterwards, landing at Wilmington, came up the Cape Fear River to Campbellton, afterwards Fayetteville where they located. Here William Williamson engaged in teaching while he was permitted to remain in America, but when the subject of independence began to be agitated, the British soldiers after investigation, were heard to remark that man’s head might overturn a government, and so Williamson and Rev. John McLeod, a Presbyterian minister, were taken under guard, carried to Wilmington, and placed on a vessel to be deported to Scotland. Nothing more was ever known about the vessel after sailing and it was supposed to be lost at sea.
Catherine (Campbell) Williamson and her two daughters were visiting friends near the McLauchlin home twenty miles west from Fayetteville when the husband and father were taken to be seen by them no more. William Williamson left many interesting and valuable papers and documents which would now be of considerable historical value, but all were lost in the confusion of the times, except portions of a diary which he kept before leaving Scotland.
If anyone can help me make sense of this - the who in the world was Catherine and who in the world was William part - that would be excellent.
