William N. Irwin, a medical doctor, held land at Beihy, parish of Cloone, barony of Mohill, county Leitrim, at the time of Griffith's Valuation. William N. Irwin of Terkeenan, county Monaghan, is recorded as holding over 800 acres in county Leitrim in 1878 as well as property in Armagh and Longford. He served as a magistrate in county Monaghan. McParlan records Richard Irwin of Dromsalla on his list of "resident gentlemen of property" in 1802. Ephraim Irwin continued to hold small amounts of land in the parish of Carrigallen at the time of Griffith's Valuation.