Portland Park was the home of the Stoney family since 1776 when it was purchased from the Earls of Antrim. At it's peak the estate comprised 2778 acres. The present ruin was built in the early 1800s at a time when many of the large houses were built in Ireland following a boom in agriculture due to the Napoleonic wars. The house was built in a strange location close to the Shannon instead of being located higher up on Portland Hill. This was probably part of the reason why Major Charles Kemble Butler Stoney renovated an old stone built school and moved in about 1928. He had been a Major in the Royal Flying Corps during WW1. He had joined the territorial army in 1896 while studying for a BA degree at Trinity College Cambridge. He became a member of the Institute of Naval Architects in 1912 and was appointed an Equipment Officer with the wartime rank of Major. He inherited the house when his father Walter Charles died in 1919. His elder brother Lieut B Butler Stoney died in 1917. After WW1 death duties were very high and apart from the land around the school the remaining 768 acres was divided by the land comission, mostly into uneconomic 20 acre units. Previously land had been purchased by tenants under the Land Purchase Acts of the late 1800s.

The house was given to Emmanuel House Rathgar in 1938 as a home for their orphanage but was burned down by an armed gang early on the day the first children were to arrive. RC Church involvement in the incident was suspected because of at least one fairly similar event subsequently. The house was a ruin for many years until partly restored by a German builder in the 1970s. It was then operated as a hotel by a Dutch Group and later by an Irish individual. The bedroom wing which was attached to the south of the old building was subsequently burned down and the building is again a ruin.