he cleft basalt rock at Dumbarton has been fortified for over fifteen centuries, 'a high rock, perpendicular and bare,' as Dorothy Wordsworth described it after climbing to the top with her brother, William Wordsworth, and fellow poet, Samuel Taylor Coleridge, in 1803.

Today, the most conspicuous buildings on the rock are the Governor's House, on the site of the medieval gatehouse, and the King George Battery, both built in 1735. The earliest surviving structure is the 14th century portcullis arch, but there is evidence for the existence of a fortified settlement as long ago as the 5 century, and extensive medieval ramparts are visible in an engraving of 1693 by John Slezer. The fortifications were repeatedly destroyed, rebuilt and elaborated as armies fought for control of this great strategic site, controlling access to the Vale of Leven, and commanding the entrance to the Firth of Clyde. The early name for the rock was Alcluith, or Alt Clut, meaning 'Clyde Rock'. From the 5 century until 1018, it was Dun Breatan, the fortress of the Britons, and in 1489, the great siege gun, Mons Meg, was brought from Edinburgh Castle and trained on the rock.

It was from Dumbarton in 1548, after the Battle of Pinkie, that the 5 year-old Mary, Queen of Scots, left for France and marriage to the Dauphin. After the Act of Union in 1707, and the Jacobite Rising of 1715, it was decreed that Dumbarton should be maintained as one of the key fortresses of Scotland, together with Edinburgh, Stirling and Inverness. After the 'Forty-Five' and Prince Charles Edward's disastrous attempt to regain the crown for Scotland, all the Government's Lowland bases overflowed with men. Between Spring and autumn, many of these soldiers were deployed on 'Highland duty,' working on the roads, or enforcing peace. By the end of the 18 century, these brave soldiers and tenacious Highlanders had become an indispensable backbone of the British army in India.