A little bit more info while I'm checking:
From the MI booklet produced by D & G FHS:
'The three medieval parishes of Lochelletun, Galston and Kirkcormac were united in 1567-1615, with the parish church established at Kelton, the most notherly of the three which was in the most fertile part...........after the level of the loch was lowered in 1765 the estate of Carlinwark became populousat at Causewayend a town grew. In 1792 the owner, William Douglas of Galston, made the town a burgh of barony called Castle Douglas'
Gadget