With any ancient history there needs be some conjecture in order to fill in the blanks. In an attempt to eliminate any guesswork, conjecture or wishful thinking, this is what I believe we know to be true of the history of the family McUisdean, in all its spellings and pronunciations.
1) Hugh of Sleat was a real historical figure, known also as Uisdean McDonald, Austin Roy, Hucheon of the Isle of Slet, and many other variations of his name. He ruled, without any doubt, from Dunscaith Castle, on the Sleat Peninsula of the Isle of Skye, off the west coast of Scotland. His sons were McUisdeans.
2) Based on his father's marriages and locations, Hugh seems to have been born in 1436, although this date could move one way or the other a bit. Based again on his father's history, it would seem likely that Hugh was born at Dingwall Castle not far from Loch Ness.
3) Hugh is said, in every record of him, that he died in 1498. A chief of Clan Donald died at Paisley Abbey in 1498 and we know for a fact it was not Hugh's brother, John, last Lord of the Isles, who died in 1503. We can't be absolutely sure that it was Hugh who died at Paisley Abbey but there is no other likely contender - no other Clan Donald chief of that period. He is said, by all accounts, to be buried at a place called Sand on the Isle of North Uist. There is a churchyard burial ground there called Clachan Shanda, or " the community and church of Sand," in the English language, and so this would seem to be the actual burial place of Hugh.
4) We know that Clan Donald considers our name as a sept of their clan. We know that we were designated, through DNA testing, as a "clear subset" of one group of McDonalds, and that, at least in some cases, we match DNA with other names historically linked to Hugh, including Martin, Harris, Hutchinson and Houston, all names which are also considered septs of Clan Donald.
5) We know that our name, if not our actual bloodline, comes from Hugh of Sleat. His first four sons are recorded with variations of our name. His first son is named with three variants, and his second son with two. His third and fourth are recorded with one version of the name. At least one later generation used Mac Uisdean. There is no other source given for our name and so at the very least we can be sure this is where the name originated.
6) Hugh's second son married a distant cousin from County Antrim, Ireland, meaning he likely traveled there, perhaps more than once. His son (being Hugh's grandson) definitely went there as recorded in three separate histories and an epic poem. The same general area where Hugh's grandson, and Hugh's great-grandsons, landed is where a handful of more modern spellings of the name appear within just a generation or two.
7) We know that the current chief of Clan Donald of Sleat uses the patronymic of McUisdean, and that Chief of Sleat is now a County Antrim title, not a Scottish title.
8) We know that the lowland Scottish McQuistons say their families came over from Ireland. Most McUisdean branches in America also came from Northern Ireland.
9) We know that on the Isle of Skye is located Caisteal Uisdean and the town of MhicCuithean. In lowland Scotland is the McQuiston Golf Cup and McQuiston Bridge. In Northern Ireland is McQuiston Church and the former McQuiston School. And so we can be sure that the Isle of Skye, the North of Ireland, and the lowland area of Scotland, between the west coast and Glasgow, were the haunts of our family, before coming to America.
10) Tradition from as far back as Leona McQuiston's book of 1937, and of her helper, Ed McCuistion (who began his research in the 1800s), says that the above history is what has been passed down from generation to generation. It is also alluded to in many other books not written by family members, but rather by clan or Scottish/Irish historians.