It is built on Rock Island Point at the North side of the entrance of Crookhaven. It was originally requested by the local boatmen and fishermen. A memorial from the inhabitants generally was presented by the Coast Guard, stating that the Alderman Rock would be the proper position for the light; however, Mr Halpin did not approve of that rock on account of its friable conditions, but recommended the present site in preference.
The Trinity Board gave their statutory sanction on 31 October 1838.
The buildings were designed by the late George Halpin Esq. The tower and dwellings were build by Mr John Cotter, Contractor. The entire cost up to the end of the year 1844 when quite complete was £9,151.7.0. which includes all buildings, rock cutting, roads and apparatus etc. as well as the cost of maintenance to that date.
The light was a steady white light, showing red across the Alderman Rock, to Streak Head, from NW ½ W to rounds to N¼ E dioptric of the 3rd order. This light was first exhibited on the night of 4th August 1843 and in 1867 it was improved and changed to dioptric.
The shore dwellings for the families of the Lightkeepers of the Fastnet Rock were based here and the light was in the charge of the Principal Keeper of Fastnet Lighthouse. In January 1953 an Attendant was appointed to look after the station.
The tower is painted white, the light is 20 metres above high water.
On the 10th December 1964 the light was changed to LFl WR 8 secs with a range of 13 nautical miles for the white light and 11 nautical miles for the red light. The sectors are as follows:
White: Over Long Island Bay to 281°
Red: 281° - 340° (59°)
Inside Harbour Red: 281° - 348° (67°)
White: 348° towards North shore
The station was converted to electric power in 1978.