The site on Barrack Street once held what became known as Custume Barracks, a garrison complex whose earliest phase was thrown up in 1691 to accommodate a remarkable concentration of troops: temporary quarters for a thousand cavalry and fifteen hundred infantry, built in the immediate aftermath of the Williamite Wars as the new political order set about consolidating its hold on the midlands.

Within a few years that improvised arrangement gave way to something more permanent. Around 1697, cavalry stables, a riding house, and an infantry barracks of four blocks were constructed on the site. A riding house was a covered training arena for horses and riders, a standard feature of any serious cavalry establishment of the period, and its presence here points to the scale of the operation. That infrastructure did not survive indefinitely: all of it had been demolished by 1793, leaving the ground free for later development. The Church of Saints Peter and Paul, built in 1930, now occupies the south-eastern corner of what was once the barracks precinct, while the Garda Station and government offices that went up between 1935 and 1947 cover another portion of the original extent. The street name is one of the few things that makes the history legible from the outside.