The name Mar originates from one of the seven ancient kingdoms that made up Scotland. The Kingdom of Mar lay between the Rivers Dee and Don in what is now Aberdeenshire. The Earls of Mar supported Robert I and the 6th Earl's daughter, Isabel, became Robert's first wife. The 7th Earl strengthened the alliance further by marrying Robert's sister.
As Regent of Scotland in 1332 Donald Mar faced the English army after only ten days in the post. Despite outnumbering the English he was defeated and was among those slain in a night raid.
After a marriage to the Stewart family there were many disputes over the earldom until the matter was settled by Queen Mary in 1565, who restored the rightful heirs to their inheritance.
The Mars fought for the Royalist cause but were not keen supporters of Charles I. They were also loyal Jacobites, regaining the earldom in 1824 which had been forfeited after the uprising failed.