According to the RCAHMS record, a cairn crowns the summit of this mountain. It's covered in grass and has a bit of a hazy outline, and has a modern marker cairn added on the top.
The New Statistical Account of Scotland says:
The most remarkable hill [of this parish] is Cairnharrow, lying partly in Anwoth and partly in Kirkmabrec, the height of which is 1100 feet. The soil on it is of a mossy kind, covered with heath intermixed with graass, and not much encumbered with rock. Cairnharrow is the highest eminence within twent miles, with the exception of Cairnsmore in the parish of Minnigaff; and its summit commands one of the most interesting and extensive views imaginable, -- not merely the adjacent country and bays of Wigton and Fleet, but the Isle of Man, part of Cumberland, and the high land on the coast of Ireland.