Probably the earliest authentic history of Mackintosh is traceable to Shaw or Seach MACDUFF, a Cadet son of the third Earl of Fife. The son of MACDUFF, for his support of Malcolm IV, was awarded the lands of Petty and Breachley in Invernesshire and was appointed Constable of the Castle thereto. Assuming the name "Mac-an-Toisch", which means "Son of the Thane or Chief", he began his own Clan. The Clan support of James I in 1429 resulted in large tracts of land being settled on the Mackintoshes. Clan Mackintosh was involved in the "Battle of the Thirty", a mass trial by combat, which was held under the judicial control of the King in 1396 on the North Inch of Perth, in which Clan Mackintosh regained all lands taken from the Shaws.
Clan Mackintosh supported the King in the revolt of 1688, but in 1715, The Mackintosh gave its support to the Jacobite Rebellion. At the "45 Rising", Angus, who held a commission in the Black Watch, could not, in honor, raise the Clan for Prince Charles Edward. His wife, Lady Ann (Colonel Anne), raised the Mackintosh Battalions for Clan Chattan in support of "Bonnie Prince Charlie." The Chattan Regiment distinguised itself at the Battle of Culloden under the leadership of the Chief of the MacGillivray's and was one of only two Scottish Regiments which did not lose their colors. Earlier, following "Colonel Anne's" tactics, five Mackintoshes, under the leadership of Fraser, the Blacksmith, had routed 1500 of Lord Louden's Troops who were approaching Moy Hall in attempt to capture Bonnie Prince Charlie.