The transactions relating to the earlier history of this Earldom have been embraced in the articles dealing with the Sea-kings of Orkney, reguli of ancient Orcadia, which term will be found convenient to define the territories under their rule.
The Orcadian Jarldom consisted of two principal parts - Insular and Scottish. The former comprehended the twin archipelagoes of Orkney and Shetland, bestowed on Rognvald "Riki" of Moeri Jarl, by King Harald Fairhair of Norway, about the year 871 of the Christian era. Insular Orcadia was generally referred to as the Earldom of Orkney, of which the Lordship of Shetland was an appanage or secundogeniture - lost in 1196 by Earl Harald II, "the Wicked", not to be recovered till the occasion of the accession of Earl Henry I, first of the House of Saint-Clair. The Isles have also been described as The Countries of Orkney and Shetland.
Scottish Orcadia, or Caithness, was acquired by joint conquest in 871, by two celebrated warriors - Thorstein the Red, Prince of Dublin (son of Olaf the White, King of that city, hereafter the Irish metropolis), and Sigurd the Sea-King, brother of Rognvald, Earl of Moeri, from whom he had already received Insular Orcadia in free gift. Sigurd had been flag-captain to King Harald Fairhair in his western cruise of conquest and colonisation, and was descended from the deified hero Thor, first-born son of Odin. Thorstein and Sigurd, although effecting a conquest of Caithness so permanent as to transmit their honours for over a millenium to their direct heir-male of line - John VI, 55th Earl, 17th of the surname of Sinclair - both yielded up their lives in battle with the Scot. The valour of Thorstein has been gloriously celebrated in verse by the poet Motherwell in "The Sword-Chant of Thorstein the Red". After his death his rights to the conquered country passed to his daughter Groa, married to Earl Duncan; Sigurd being succeeded by his son, Earl Guttorm, who dying without issue, his dominions in Caithness seem to have lapsed; while those in the Isles went in succession to his kinsmen Hallad, Einar, Arnkell, Erlend, and Thorfinn Hausakliuf, "Splitter of Skulls". Thorfinn, 8th Earl of Insular Orcadia, by marriage with Grelod, or Grelauga, heiress of Groa and Earl Duncan, became 5th Earl of Caithness, uniting it to his Island dominions.
By Grelauga Earl Thorfinn had five sons, his successors - Arnfinn, Havard, Ljot, Skuli, and Hlodver (Ludovic). Arnfinn, 6th Earl, espoused Ragnhild, daughter of Eric Bloodaxe, ex-King of Norway and of Northumbria. After the death of Arnfinn, which event it was supposed had been achieved by Ragnhild, his brother Havard hazarded an alliance with her; and incredible as it may seem, although she was suspected of complicity in connection with the death of Havard, his brother Ljot had the hardihood to marry her also. Skuli now laid claim to a portion of Orcadia, and received substantial assistance from the then (974) King of Scots (Kenneth III), who created him a belted Earl and furnished him with a strong army, beside which he had the support of a Scottish chief, Magbiod. This creation is the first instance of Scottish interposition in Caithness affairs. Ljot and Skuli engaged in battle, Skuli falling and Ljot being mortally wounded. To them succeeded the surviving brother Hlodver, uniting in his person the Caithness claims of both Grelauga and Thorfinn.
Hlodver, 8th Earl, like his father was a great warrior, and while roving in the West became enamoured of Audna, daughter of an Irish royalet, Carroll, King of Dublin (Kiarval, King of the Ivar). The antiquity of the Earldom of Caithness can best be realised by pointing out that the foregoing Earls were contemporaries of those Scottish sceptred shades - Constantine II, Aodh, Eocha, Grig, Donald IV, Constantine III, Malcolm I, Indulf, Duff, Culen, Kenneth III, Constantine IV, Malcolm II, etc.; but there is no record of the writs of these royalties running through Caithness, which was practically independent, the Jarls thereof having Ross and Moray under their sphere of influence: laying the Hebrides under tribute, governors being appointed in those regions for the collection of taxes; and exercising not only in Caithness, but also in Insular Orcadia, all jura regalia, subject only with regard to the latter to occasional interpositions of the monarchs of Norway.
Earl Hlodver had - with a daughter Hvarflod, married to Earl Gilli of the Suderies - one only son, Sigurd II, the Stout, 11th Earl, who married secondly Anleta, a daughter of King Malcolm II of Scotland; and falling at Clontarf in 1014, was succeeded by Thorfinn II, son of that marriage, then in minority. Thorfinn was the greatest of all the Earls of Orcadia, and his alliance it was with "the peerless Macbeth" which helped to elevate that Prince to the Scottish throne. By Ingibiorg, [She married (2nd) King Malcolm Canmore] daughter of Earl Finn Arnason, Thorfinn the Great left two sons, the exiled Earls Paul and Erlend, both of whom died in captivity in Norway in 1103, being succeeded in Caithness by Hakon. 15th Earl, son of Paul (by a daughter of the Norwegian Earl, Hakon Ivarsson and Ragnhild, daughter of King Magnus the Good), who dying in 1122 left two sons - Harald the Orator, poisoned in accident (1127) by his mother Helga; and Paul II, the Silent, abducted to Atholl (1136) by Sweyn, a noted Orcadian Viking. Hakon left also two daughters - Margaret, married to Madach, Earl of Atholl, a member of the Royal Celtic Line of Scotland, and nephew of King Malcolm III; and Ingibjorg, married to Olaf, King of the Hebrides and Man. On the death in 1156 of the 15th Earl, Erlend II, the Younger, son of Harald the Orator, the male line of the family of Sigurd the Sea-King came to an end.
A few instances of interpolated succession now occur. From a Dunfermline record it appears that a Scottish noble, MacWilliam, had the title of Earl of Caithness, 1129-1160; and on the deposition of Paul the Second, Rognvald, a son of Gunnhild, daughter of Erlend the Exile, effected an occupancy of the Isles, and presently, by arrangement with the guardians of young Harald of Atholl (son of Margaret of Orkney), he acquired the Caithness possessions also. All Orcadia was to be held jointly by Rognvald and Harald, but under the sole rulership of Rognvald. Rognvald the Rhymer, 20th Earl, was a celebrated Crusader and pilgrim-poet.His verses are still extant in the library at Opslo [Christiania]. He fell in 1158, a victim to the private vengeance of one of his turbulent subjects and the veneration of posterity has enrolled him in the calendar of saints. He left an only daughter, Ingigerd, married to Eric Stagbrellir, whose son, Harald III, 22nd Earl, in 1196 succeeded in obtaining the half of Caithness from King William the Lion. This title Harald II of Atholl was in no way inclined to allow, and a battle ensued at Clairdon in Caithness, where young Harald, after distinguishing himself by his valiant actions, found an early grave (1196).
Harald II the Wicked was now in undisputed possession of Orcadia, which then comprised Orkney, Shetland, Caithness, Sutherland, and Strathnaver. He was twice married, first to Afrecca, daughter of the Earl of Fife, by whom he had a son Henry, reputed Earl of Ross by the contemporary Saga annalists; and Hakon, who perished in battle with the Irish. By his second wife Gormlath, a daughter of Earl Malcolm MacHeth of Moray (ex-Bishop Wimund), the pretender to the Scottish throne, he had numerous issue, the surviving sons being his successors - David, 23rd Earl, died 1214; and John, 24th Earl, killed in 1231, whose son Harald, the Master [heir apparent] of Orcadia, had predeceased him, being lost at sea some years antecedently.
The Orcadian Earldoms now pass to one Magnus, who is assumed to be the second son of the Earl of Angus; but as the Earldom of Angus goes immediately to an heiress, it is difficult to reconcile that fact with the Orcadian and Caithness succession. It may be that Magnus, Earl of Orkney and Caithness, married twice, having issue by the first marriage his successor, and marrying secondly the heiress of Angus, thus becoming Earl of Angus by right of his wife, and accounting for his appearance in 1232 as Magnus, Earl of Angus and Caithness. By the second marriage with the heiress of Angus, Earl Magnus may have had the one daughter, Matilda, Countess of Angus in her own right, who married first John Comyn (1242), and secondly Gilbert de Umfraville, in which latter family the Earldom of Angus continued for some length of time. The foregoing is, however, only speculative, and the accepted version is that Magnus, second son of the Earl of Angus, became 25th Earl of Caithness as heir-at-law to his predecessor, Earl John. To Magnus succeeded Gilbride I and Gilbride II, whose son, Earl Magnus II, was the 28th in succession. He was with King Hakon at Largs, and entered into a contract of privileges with Magnus VI of Norway. His son, Magnus III, received the title by investiture at Tunsberg in 1276, and was one of the seven earls of Scotland who, in 1283, agreed to recognise Margaret, "the Maiden of Norway", as next successor to the Scottish realm. Dying in 1284 without issue, the Earldom passed to his brother, John II, 30th Earl. In 1291 Earl John had a safe-conduct from King Edward I of England to report the circumstances of the death of the Princess Margaret on the Orcadian Coast. In 1297 he recognised Edward I as Paramount of Scotland. The seal he used on that occasion was a ship with a tressure [border] of fleur-de-lys around it. In 1299 he was betrothed to Ingibiorg, Princess of Norway (daughter of King Eric by Isabel Bruce, daughter of Robert Bruce, Earl of Carrick), but the betrothal does not seem to have resulted in marriage. He died before 1312 as his son, Magnus IV appears then on record as Earl. In Magnus' time, and presumably in his favour, the King of Norway restricted the use of the comitial title to the king's sons and the Earl of Orkney. He was present at the Treaty of Inverness, 1312, between Robert I of Scotland and Hakon V, and in 1320 subscribed the famous letter to the Pope. Next year (1321) Henry de St.Clair appears as Ballivus in Caithness, which is the first notice of the Roslins in those parts. In 1329 Katherine, Countess of Caithness and Orkney, executes deeds in viduilate, and the Caithness possessions of Earl Magnus are found inherited by the Earl of Stratherne and Simon Fraser, reputed ancestor of the Lovats.
It is surmised that Malise III of Stratherne, when in apparency only, married Matilda, daughter of Earl Gilbride II ii of Orkney and Caithness, and had issue Matilda contracted at the age of nineteen, in 1293, to Robert de Thouy, and Malise IV, seventh Earl of Stratherne, born about 1272. Malise IV of Stratherne succeeded, on the death of Earl Magnus IV, to the Earldoms of Orkney and Caithness, thus uniting in his person three important Earldoms at a time, when there were only about twelve in existence in Scotland. He appears in 1331 as possessed of the fourth part of Caithness. Falling at Halidon, in 1333, he left issue a daughter, Joanna, and his successor Malise II of Orkney and Caithness, V of Stratherne. This puissant prince married, first, Johanna de Menteith, by whom he had a daughter Matilda, married to one Weyland de Ard; and secondly, the Lady Marjory of Ross, by whom he had, with other issue Annot (died without issue), married to Erengisle Suneson, and Isabella, ancestress of the St.Clairs hererafter Earls. Dying in 1344 or 1345, an interval of confused succession occurs. His Earldom of Stratherne being (it seems) a male fief, reverted to the Scottish Crown, and was granted in 1345 to [his cousin] Maurice Moray (died 1346), who had married Joanna, Countess-Dowager of Atholl, styled also Countess of Stratherne, Warrenne, and Surrey, and reported variously to be mother, stepmother, sister, wife, widow, and daughter of the last Earl Malise. It then passed to Robert the Steward (brother-in-law to Malise), who afterwards, on becoming King of Scotland, bestowed it on his brother David. The Earldom of Orkney was, in 1353, conferred on Erengisle Suneson, a Swedish noble, by right of his wife Annot de Stratherne, but she died before 1357, in which year Erengisle suffered forfeiture. Earl Malise had executed an instrument at Inverness on the 25th May 1344, securing the Earldom of Caithness to his daughter Isabella, under the protection of her uncle, William, Earl of Ross. Isabella presently married Sir William St.Clair of Roslin. The said charter was confirmed at Scone by King David II 12th May 1362, and in 1367 it is noted that there remain in the bands of Sir William Keith £10 annual rent charge on the Earldom of Caithness by reason of ward of the heir of William St.Clair. Notwithstanding the incontestable rights of Isabella, Lady St.Clair, to the Earldom, as instructed by these charters, through Court intrigue and covetousness the possession was assumed to have devolved upon Alexander de Ard, son of Matilda de Stratherne, the eldest co-heiress of Earl Malise II Alexander de Ard, as heir-general, should have inherited the Earldom of Stratherne, but that fief was apparently limited to heirs-male, and a new creation had probably before birth of de Ard been given in 1345 to Sir Maurice Moray, who, dying without issue in 1346, the Earldom was granted anew to Robert Stewart, who, in 1370, became King of Scotland. Reluctant to relinquish the revenues of the Earldom, and yet desirous to compensate de Ard, who had been superseded in Orkney first by Erengisle Sunesson, next by the St.Clairs, and finally by the Norwegian Crown, the Scottish sovereign permitted him to acquire possession of Caithness at the expense of Lady St.Clair and her children, then in minority. In 1375 Alexander de Ard resigned to King Robert II his rights to Caithness, Stratherne, and all other lands in Scotland, and eventually died without issue.
King Robert II thereupon created his brother David Earl Palatine of Stratherne and Caithness, but the latter dying without issue male, the Earldom of Caithness returned to the Crown, and was bestowed on Walter Stewart, Earl of Atholl, in 1424, who forthwith assigned it to his son Alan, on whose death, at Inverlochy, in 1431, it continued with his father till his execution in 1437, when reverting to the Crown it remained in commission for some years. In 1450 it was granted to George Crichton, Lord High Admiral of Scotland. He died without male issue in 1455, in which year the Earldom was restored to the direct line in the person of William Saint-Clair, 44th Earl of Orkney, and has ever since continued in his house.