From A Topographical Dictionary of Ireland, 1837
FORTH MOUNTAIN, an extra-parochial district, partly in the barony of FORTH (from which it derives its name), partly in that of BARGY, and partly in that of SHELMALIER, county of WEXFORD, and province of LEINSTER, 2 miles (S. W.) from Wexford; containing 1102 inhabitants. During the disturbances of 1798, this place was selected as a military station by the insurgents, who encamped their forces, amounting to several thousands, on the north-eastern extremity of the mountain called the Three Rocks, previously to their attack on Wexford. To reinforce the garrison of that town, a detachment of the Meath militia, with a party of artillery and two howitzers, was sent from Duncannon Fort, under the command of Capt. Adams, which on passing near the foot of the mountain was intercepted by a large party of the insurgents, the whole detachment cut to pieces, and the howitzers and ammunition captured.
Immediately afterwards, Lieut.-Colonel Maxwell marched out from Wexford with 200 of the Donegal regiment and about 150 of the yeoman cavalry, to support the 13th regiment commanded by Major-General Fawcet, which was expected from Duncannon Fort; but the Major having heard of the disaster at the Three Rocks, fell back with his regiment, after having advanced as far as Taghmon. Colonel Maxwell, who had been also apprised of the destruction of the detachment, collected his forces and advanced towards the insurgents, to co-operate with Major Watson, of whose retreat he was ignorant. On his arrival near the Three Rocks, he was attacked by a numerous body of the insurgents, who rushed down from the mountain with a view of cutting off his retreat; but they were repulsed by a steady fire from the Donegal regiment, and Colonel Maxwell seeing no appearance of Major-General Fawcet, and finding his forces exposed to great risk without any prospect of advantage, retreated to Wexford.This place now became the chief rendezvous of the insurgents, whose numbers were so formidable, that it was considered necessary by the garrison and inhabitants of Wexford to abandon the town, of which the former immediately took possession.
The mountain rises two miles south-west of Wexford, to an elevation of about 500 feet above the level of the sea, and extends upwards of three miles in the same direction, having a mean breadth of nearly two miles; it is chiefly composed of quartz, with a slight covering of alluvial soil, partly under cultivation and partly producing only furze and heath, which serve for fuel. Many of the peasantry have located themselves on its sides, and by immense labour have cleared away the stones from a considerable tract and converted it into good arable land, of which they remain in undisturbed possession. Its summit rises into a variety of fantastic forms, and commands a grand and very extensive prospect.
In the R. C. divisions the sides of this mountain are included in the respective districts or parishes immediately adjoining. On that part which borders on Kilmannon is a public school, in which about 160 children are educated.