In the 12-14th Century most of the land around the Loch belonged to the Earls of Lennox. This powerful family owned Balloch Castle, which is still visible to this date within the present castle grounds. They also owned castles on Inchmurrin and at Boturich. As was customary, the Earls granted lands to favoured families - Arrochar and the north-west to the MacFarlanes, Luss and the south-west to the Colquhouns. The Buchanan and Grahams had land on the eastern side, and the MacGregor's held sway to the north-east of Loch Lomond.
The MacFarlanes, on the rough northern land, were given to night raids on their southern neighbours cattle - hence the moon was referred to as "MacFarlanes lantern". Their castle at Inveruglas was destroyed by Cromwell, and another built on Eilean I Vow, (Gaelic:Eilean a' Bho - 'island of the cow'), where ruins can still be seen today.
The Colquhouns share a common ancestry with the Clan Lennox, their castle is at Rossdhu, south of Luss, (Gaelic:'black wooded promontory').
In the grounds of the present Georgian house there are the remains of a 12th Century Chapel, a 15th Century deer park - meadow enclosed by a ditch and a bank - and a 16th Century square keep. (Site of the Loch Lomond Golf Course). The small island of Eilean Rossdhu has the remains of an earlier castle.
The MacGregors of Argyll and Perthshire, to the north of Loch Lomond, made a raid on Luss in 1603 which was followed by a massacre of the Colquhouns in Glen Fruin - 'the Glen of Sorrow'. For this, the MacGregors chiefs were executed, and the whole Clan proscribed - dispossessed of their land and their name. To harbor a MacGregor was a punishable offence, so they became outlaws. Rob Roy MacGregor was undoubtedly the most famous.
The Buchanans originally went by the name of MacAuslane after King Anselan of Ulster who came to Argyll around 1016. For services to Malcom II, he was given the lands of Buchanan to the east of Loch Lomond, which remained in the family until 1682, when they were sold to the Marquis of Montrose.