The Macarthurs are Celts, and the family of Arthur is one of the oldest clans in Argyll, so ancient that even in remote Celtic times there was a Gaelic couplet which is freely translated, ‘the hills and streams and Mac-alpine but whence came forth Macarthur?’ The Macarthurs supported Robert the Bruce in the struggle for the independence of Scotland, and their leader, Mac ic Artair, was rewarded with lands in mid Argyll, which had belonged to those who had opposed the king. Over the years many descendants of Arthur dispersed, some settling in Skye where one family of Macarthurs set up a famous piping school and were for several generations hereditary pipers to the Macdonalds of Sleat. The most celebrated of this family was Charles, who received his piping instruction from Patrick Og Maccrimmon. Another branch of the family became armourers to the Macdonalds of Islay. Two families of Macarthurs came to the fore in the late 1400s around Loch Awe. There has been a good deal of confusion between the Macarthurs of Loch Awe and the Macarthur Campbells of Strachur on Loch Fyne. The names of some Macarthurs holding prominent positions appear in the fifteenth century in mid Argyll, and by the latter half of the sixteenth century they had gained so much land and power that their neighbours became jealous and Duncan Macarthur and his son were drowned in Loch Awe during a skirmish in 1567.

The Earl of Argyll ordered compensation to be made and appointed a nephew, John, son of Finlay, to be leader of the Loch Awe Macarthurs. The direct male line appears to have become extinct in the years around 1780. The Macarthurs of Milton, at Dunoon, had by the middle of the 1680s producea baillie in Kintyre and a chamberlain to the Marquess of Montrose in Cowal. The Macarthurs also sought their fortune abroad, and Colonel John Macarthur became military deputy governor of St Kitts in the Caribbean. A large number of the clan, many of whom fought on both sides in the Jacobite risings, left Scotland, particularly after the disaster of Culloden in 1746, eventually to settle in the West Indies, America and Canada. A Macarthur migrant from Strathclyde landed in America in 1840. His son, Arthur, fought in the civil war and was promoted to lieutenant general in the US army, while his son, Douglas, became even more well known as the commander of the Pacific Theatre in the Second World War. In September 2002 James MacArthur of Milton was matriculated at the Lyon Court as MacArthur of that Ilk.