- Various members of the Irwin family are recorded as the owners of land in county Sligo in the 1870s. McTernan notes that this branch had been prominent in Sligo social and political life in the eighteenth century, serving as magistrates, Grand Jurors and High Sheriffs. However, as the ninetenth century progressed the family tended to live out of the county, principally in Dublin. In 1883 Bateman noted B. Irwin as the owner of over 5,700 acres in counties Sligo and Donegal.
- McTernan states that John Irwin, a Cromwellian soldier, wsa granted the lands at Tanrego in the seventeenth century. The Irwin family also had property in the parish of Achonry, barony of Leyny. Turlough O'Carolan was a frequent visitor to Tanrego and composed a number of tunes in honour of the family including "Colonel John Irwin". In 1855 John Lewis Irwin offered for sale lands in the baronies of Tireragh, Leyny and Carbury, including Tanragoe. The estate was acquired by the Olpherts and later the Verschoyle families. The house was occupied in the 1850s by Capt. Richard Olpherts. The house and lands at Barnabrack were also part of the Irwin estate.