St Mary's Loch, Yarrow par., Selkirkshire, at border of Peeblesshire, 16 miles SW. of Selkirk and 15½ miles NE. of Moffat; is 3 miles long and ½ mile in extreme breadth, lies 814 ft. above sea-level, and at its E. extremity discharges Yarrow Water. It is celebrated in the poetry of Scott, Hogg, and Wordsworth.

(John Bartholomew, Gazetteer of the British Isles (1887))