The following lengthy quotation about the parish of Gladsmuir comes from the Ordnance Gazetteer of Scotland, edited by Francis Groome, published in London, 1903.
Gladsmuir, a village and a parish in the W of Haddingtonshire. The village stands 355 feet above sealevel, near the eastern verge of the parish, 2½ miles SSE of Longniddry station, on the Haddington branch of the North British railway, 4 W by S of Haddington, and 3½ E of Tranent, with a post office under Macmerry. Crowning the ridge between Haddington and Tranent, it commands a superb panoramic view of the Lothians, the Firth of Forth, and the southern shore of Fife.
The parish, constituted in 1692 out of portions of Haddington, Tranent, and Aberlady, contains also the villages of Longniddry, Samuelston, and Penston. It is bounded NW by the Firth of Forth, N by Aberlady, E by Haddington, S by Pencaitland, and W by Tranent. Its utmost length, from N to S, is 4¼ miles; its utmost breadth is 4 miles; and its area is 7165¼ acres, of which 120¾ are foreshore. A small burn, running to the Firth, traces much of the Aberlady border; another traces for 1¾ mile the boundary with Tranent; two others rise in and traverse the interior; and the river TYNE winds 1¾ mile east-north-eastward along the Haddington border. The coast-line, 1 mile long, is low but rocky; and from it the surface rises gently to 371 feet at Penston and 400 at the south-western corner of the parish, whilst sinking again south-eastward to 190 feet along the Tyne. So much of the area was in a marshy condition as to look almost like a continuous fen, but now has been so thoroughly reclaimed as to be everywhere in a state of high cultivation. The ridgy tract, too, was for ages an open moor, but that likewise has been well reclaimed. The rocks belong chiefly to the Carboniferous formation, but are intersected, from E to W, by a remarkable trap dyke, which has been largely quarried for road metal, and for building has abundant sandstone. Limestone and ironstone have been worked; and coal abounds of excellent quality, occurring in some places in seams from 4 to 5 feet thick. It seems, in the vicinity of Penston, to have been mined for upwards of five centuries. Fireclay also is plentiful. The soil is sandy on the immediate seaboard, a fertile loam towards Longniddry, clayey in the middle tract and loamy along the Tyne. About 200 acres are under wood; nearly 1200 are in pasture; and all the rest of the land is either regularly or occasionally in tillage. The mansion of the Douglases of Longniddry, who acted a distinguished part in the Reformation, and invited John Knox to their home when he was driven away from St Andrews, is now represented by only a low round mound. A ruined chapel, called John Knoxes Kirk because the great Reformer sometimes preached in it, stands a little E of Longniddry village. A church was built, in 1650, at Thrieplaw, near the boundary with Pencaitland, but on the constituting of the parish, fell into disuse, and has utterly disappeared. William Robertson, D. D. (1721-93), who became Principal of Edinburgh University, was minister of Gladsmuir from 1743 to 1758 and wrote here the greater part of his "History of Scotland"; and George Heriot (1563-1624), the founder of the hospital that bears his name in Edinburgh, was the son of a native of Gladsmuir, and himself has been claimed as a native. Under PRESTONPANS is noticed the battle sometimes called of Gladsmuir. ELVINGSTON is the chief mansion. Gladsmuir is in the presbytery of Had dington and synod of Lothian and Tweeddale; the living is worth £300. The parish church, at the village, a handsome edifice of 1850 and successor to one of 1695, was destroyed by fire in 1886, and afterwards rebuilt. Four schools - Gladsmuir, Longniddry, Macmerry, and Samuelston - with respective accommodation for 113, 144, 140, and 61 children, have an average attendance of about 50, 90, 100, and 30, and grants of over £40, £80, £70, and £35. Valuation (1879) £18,648, 6s., (1883) £16,250, 18s., (1892) £13 044, 19s. 5d. POP. (1801) 1460, (1831) 1658, (1861) 1915 (1871) 1863, (1881) 1747, (1891) 1604