Once an entire chain of castles stretched up the valley of the Nith below these hills, providing a main route from the Solway Firth to central Scotland. Morton Castle has stood on this naturally defensive site since 14C, overlooking the verdant Nith valley and Drumlanrig Castle. More recently, Morton Castle has become linked with John Buchan's classic spy thriller, 'The Thirty Nine Steps', written in 1915. Morton Castle was chosen as a location for the 1978 film version starring Robert Powell.