- This branch of the Mahon family were established at Cloonfree, parish of Cloonfinlough, county Roscommon, from 1735 when Bartholomew Mahon was granted a lease, renewable for ever, by Thomas and Elinor Mahon of Strokestown. In 1703 Bartholomew Mahon of Strokestown had purchased part of the forfeited estate of Edward and John Boynton in the barony of Roscommon. At the time of Griffith's Valuation William Mahon had land in the parishes of Bumlin, Cloonfinlough, Kilcooley, Killukin, Ogulla, barony of Roscommon, some of it held by the Court of Chancery. The Clonfree estate of Bartholomew Mahon, "a lunatic", was advertised for sale in March 1860. It amounted to 1,757 acres in the barony of Roscommon. In the 1870s William Mahon owned 800 acres in county Roscommon. Part of Cloonfree, the estate of Matthew Ryan, was advertised for sale in March 1879.