Rockhill House is a 30-room period building originally built as a manor house in the 17th century for the gentry. Captain Thomas Chambers is the earliest recorded occupier of the house in 1660. The present structure dates from 1824 and is a listed building. Rockhill House was occupied by The Irregulars during the Irish Civil War. They were removed from the building by a pro-treaty crowd who were led by Letterkenny native James McMonagle. Rockhill House which houses the barracks was later privately owned by Sir Charles John Stewart. His two sons were killed during World War I. He sold the building in October 1936, through selling agent John King Robinson, due to the fear of attacks from the Irish Republican Army.