Scottish baronial as a style is a Victorian invention - turrets, corbelled corners, crow-stepped gables, all borrowed from sixteenth-century Scottish tower houses and rebuilt at municipal scale. It suited a country that was building its civic identity out of historic borrowings. The Portrush Town Hall is one of the lesser known of Lanyon, Lynn and Lanyon's commissions, but it has a particular Antrim character, sitting on Mark Street like a small Scottish keep that has come over the water with the herring fleet. The building is a Grade B+ listed structure today. In 1930, it was extended in the same style by Hugh Taggart of Ballymoney, working to a design by the town surveyor Albert Clarke, at a cost of £4,000. The northeast extension added a doorway with voussoirs and colonettes and the words "Portrush Town Hall" painted into the tympanum - a small piece of ceremony for what was, at heart, a working civic building.

In the strange peace that followed the truce of July 1921 between the Irish Republican Army and the UK Government, Northern Ireland had to invent itself as a jurisdiction. In August 1921, in the Portrush Town Hall, Sir John Ross - the last Lord Chancellor of Ireland - swore in Denis Henry as the first Lord Chief Justice of Northern Ireland. A new state needed a chief justice and a chief justice needed an oath, and the oath was administered in this red brick room on the Antrim coast. The following year, on 11 November 1922, a war memorial designed by Frank Ransom in the form of a bronze figure of victory was unveiled in front of the building. Lady Macnaghten of Dundarave House did the unveiling. The names on the pedestal were the local men who had died in the First World War.

Portrush was its own urban district until 1973, when local government reorganisation folded it into the enlarged Coleraine Borough Council. The town hall stopped being a seat of government. It continued as an events venue until 1997, when the council declared it surplus and proposed to demolish it. The Planning Appeals Commission turned the proposal down. Eight years later, a £1.6 million restoration - managed by the Hearth Historic Buildings Trust, paid for by the Heritage Lottery Fund, carried out by McCloskey & O'Kane of Limavady to a design by Consarc - brought the building back into use. The restored reading room was renamed the Girvan room in honour of Paul Girvan, one of the people who had argued for keeping the place. The building reopened in 2005 and resumed its role as an events venue.

In November 2021, the comedian Shane Todd presented an episode of the BBC New Comedy Award from inside the town hall. That is the kind of thing a saved building gets to do. The hall now hosts the events a small seaside town needs - weddings, awards, comedy nights, council functions - rather than the constitutional milestones of 1921. The bronze figure of victory still stands outside. The Scottish baronial turrets still face the sea. The building is no longer the seat of any government; it is something a town of six thousand decided to keep, which is its own kind of authority.