Model of Whitecastle pile light by Ken Doherty, built from a 1927 photograph, currently on display at the Inishowen Maritime Museum in Greencastle
In general, Lough Foyle is a large expanse of water, where the River Foyle, after flowing through the city of Derry (I use the term merely because it is shorter) and its outskirts, suddenly widens out as it nears the sea. Donegal is on the west side, co. Derry is on the east side. After partition, nobody thought to decide who had jurisdiction over what but now the Lough is jointly administered.
The main channel for vessels ran along the Donegal coast and lights were erected by the Derry Harbour Board to warn ships from straying too close to the shore. From north to south and showing the date of their establishment, they were -