The Castle was historically a Campbell stronghold but is likely to have been built on an earlier McGregor of Glenstrae site. The McGregors were the dominant clan in the area until being eclipsed by the Campbells.
The Castle was held by the Campbells for 400 years and became a government stronghold in Jacobean times. The Campbells were always on the right (winning) side. At this time is was extended to include a very substantial barracks and outer walls.
With the pacification of the Highland Clans and the dispersal of the McGregors the Castle outlived its usefulness. Lord Glenorchy became the Duke of Breadalbane as the Campbells power and wealth grew and the family moved to Taymouth Castle in Perthshire (and about 200 rooms!).
At its peak the Castle was a fortress and a very grand home. A day spent at Register House in Edinburgh reveals an extremely advanced society of immense wealth and power.
The family records going back to the time of the Bruce, being lodged here at Register House. They also show that “Glenorchy” wouldn’t pay his tailor in Edinburgh.
The Castle was abandoned completely at the end of the 18th Century and then had the misfortune to be burnt out after a “lightning strike” (Most likely a stray McGregor).