- At the time of Griffith's Valuation this family held land in the parishes of Garrycloyne and Grenagh, barony of Barretts, and Mallow, barony of Fermoy, county Cork. Usher Williamson was the son of Reverend Benjamin Williamson. Arthur Williamson was Usher's brother. In the 1870s the representatives of Arthur Williamson of Mallow owned 89 acres, General Williamson and Colonel John Williamson both of Carhookeal owned 660 acres between them and the representatives of John Williamson of Knuchskagh owned 520 acres in county Cork. He was among the principal lessors in the parish of Kilmacabea, barony of East Carbery, in 1852.