The history of Coolrain, County Laois is something of a mystery. The main block looks to be early-to-mid 18th century, of two storeys over raised basement and five bays with a central breakfront. The latter features a fine cut-limestone Gibbsian doorcase approached by a short flight of steps and flanked by sidelights, with a Venetian window directly above on the first floor. On either side of the main block, and seeming to be slightly later in date, are fine carriage arches, that to the right (south-east) further extending to a small stable yard. But the carriage arches are just that and no more: there is nothing behind them and the entrances are blocked up (if indeed they were ever open). It would appear their main, perhaps only, function was to extend the house façade and thereby give an impression of greater grandeur to anyone arriving there. Who designed and/or built Coolrain (and when) is unknown, but all indications are that the original owner was a member of the landed gentry with aspirations to climb the social ladder.

At some date after its construction, Coolrain was enlarged by an extension to the rear but only on the left (north-west) side. The gable ends of the older section of the building indicate it was originally just one room deep, with the central portion extended back to accommodate a staircase hall lit by another Venetian window on the return. This window was subsequently blocked up, although one wonders why this was necessary since the extension does not intrude on its space. Aforementioned extension had a kitchen in the basement and a dining room immediately above, and looks to have been added towards the end of the 18th century. The gardens behind presumably ran down to the river Tonet not far away, but to the west of the house and yard are the remains of a little rectangular folly, presumably a tea room (since it has a small basement where the servants could prepare refreshments) from which there would have been a charming view of Coolrain.

In his 1837 Topographical Dictionary of Ireland, Samuel Lewis lists Coolrain (then spelt ‘Cooleraine’) as being occupied by one T. Palmer. There were a number of Palmers living in Laois at the time, not least at Cuffsborough some eight miles to the south where the house has a similar doorcase (albeit set into a grander façade). Lewis notes that there were extensive flour and oatmeal mills in the adjacent village of Coolrain, so it may be that the occupants of the big house were involved in such a commercial enterprise. Later it was the residence of the Campion family who farmed the surrounding land until the death in 1921 of the last member to live there. Coolrain seems to have fallen into ruin subsequently, being too big and too hard to maintain for the average farmer. More recently some work was initiated on the outbuildings, but this appears to have been abandoned, and the house now stands in the middle of a field, the mystery of its origins and early history becoming ever-harder to discern.