Nobody now knows exactly where. The structure has been demolished so thoroughly, and at such an early date, that it had already vanished by the time the Ordnance Survey mapped the area in 1838. What remains is essentially an absence: a point in a chain where something briefly existed, then disappeared, leaving no trace on the landscape beyond the sandy shoreline and the fields that surround it.

Construction of the tower began in 1805, under the direction of the British Board of Ordnance, and it was still unfinished in 1806, though a signal mast had been erected by April of that year. Whether the tower itself was ever completed is not known. It formed part of a network of over eighty such stations built along the Irish coastline in the early nineteenth century, designed to relay warnings of an approaching French invasion fleet using naval signal posts, a system of flags and visual signals passed from one hilltop or headland to the next. The chain ran continuously from Malin Head in Donegal down to Dublin Bay, with the Ballygannon station sitting between Dalkey Hill to the north-north-west and Wicklow Head to the south-south-east, each roughly seventeen kilometres distant. The system was abandoned in the mid-1810s once the threat of French invasion had receded. On the west and south-west coasts, many of the towers survived into later centuries, but along the east and south-east, several were demolished early. A likely reason emerges from a letter written in 1811 by a Mr Pope, Waterford agent of the London Assurance Company, who reported that disused signal towers along the Waterford coastline were being mistaken for lighthouses by sailors navigating in poor weather, contributing to a series of shipwrecks near Tramore around 1810. His concerns apparently prompted the demolition of at least one tower in that area by the end of 1811. It is plausible that the same reasoning applied at Ballygannon, where the low coastal site, with its obstructed views in all directions, would have offered little practical use once the network closed, and perhaps posed a similar navigational hazard.