When I worked as a shipping agent in the late 1970s I had to visit this building at least twice every working day.

As the port of Dublin moved further downriver, the building's original use for collecting custom duties became obsolete, and it was used as the headquarters of the Local Government Board for Ireland. During the Irish War of Independence in 1921, the Irish Republican Army burnt down the Custom House, in an attempt to disrupt British rule in Ireland.

Gandon's original interior was completely destroyed in the fire and the central dome collapsed. A large quantity of irreplaceable historical records were also destroyed in the fire.

After the Anglo-Irish Treaty, it was restored by the Irish Free State government. The results of this reconstruction can still be seen on the building's exterior today – the dome was rebuilt using Irish Ardbraccan limestone which is noticeably darker than the Portland stone used in the original construction. This was done as an attempt to promote Irish resources.

Further restoration and cleaning of the stonework was done by an Office of Public Works team in the 1980s.