Built by the British Board of Ordnance in the early 1800s, it formed part of an extensive chain of over 80 signal stations stretching around the Irish coast from Dublin Bay to County Donegal, designed to warn of approaching French invasion fleets during the Napoleonic Wars. The square stone tower, measuring 5.9 metres on each side and rising to approximately 11.5 metres in height, retains many original features despite extensive modifications over the centuries. Its walls face the cardinal directions, with bartizans at the eastern and southern corners supported by corbels, whilst a machicolation protects the first-floor doorway on the northwest wall, originally accessed by retractable ladder.

After its military role ended around 1810, the tower embarked on a remarkable second life. In the 1880s, Lloyds of London repurposed it as a ship-to-shore semaphore station, relaying information about transatlantic shipping from the offshore island of Inishtrahull to London. The site gained international significance in 1901 when Guglielmo Marconi established a radio signal station here, successfully transmitting the first commercial radio message to the S.S. Lake Ontario in 1902. The station even participated in the radio system trials for the RMS Titanic in April 1912. During World War Two, a lookout post was constructed nearby, and the well-preserved ‘Eire Sign 80’ on the foreshore served as a marker for aircraft, indicating neutral Irish territory.

Today, the tower’s cement-rendered exterior, applied by 1902, gives it an unexpectedly modern appearance that belies its age. The surrounding complex includes remnants from various periods of use: a concrete semaphore watch house to the west, the World War Two lookout post, and foundations of earlier buildings shown in Sir William Smith’s illustrations from 1804 to 1808. Though many original window openings have been blocked and new ones added over time, the tower remains structurally sound, with two tall chimneystacks extending from its southeastern wall. From its commanding position 300 metres from the Atlantic, with unobstructed views in all directions, this resilient structure continues to overlook the waters it once guarded, embodying two centuries of Ireland’s coastal defence and communications heritage.