The Castle of St John sits in a prominent position in the centre of Stranraer. Built in the sixteenth century this is a particularly fine example of the type of tower house built and used by Scottish Lairds in the sixteenth and seventeenth centuries.

The Castle of St John was built around 1500 by the Adairs of Kilhilt, one of the most powerful families in Wigtownshire. In the late 1670s it was used as a military garrison for the government troops commanded by John Graham of Claverhouse. In the Victorian period it was used as a jail. 

The fascinating story of the Castle and its many inhabitants can be found in the exhibitions on site.