At Ireland's oldest castle built by the Norman Crown in 1185, the mill has been there just as long.  In 1869 it was transformed from a mill that fed and clothed knights to a mill that clothed gentlemen.

John Mulcahy led this vision.  Ardfinnan had a strong tradition of wool spinning and weaving in the cottages surrounding the castle, but no organised industry.  By converting the castle's flour mill he gave employment to the skilled villagers and supported the shepherds.  In days gone, the original mill on the bridge was patronised by the charitable Knights Templar and Knights Hospitaller who could banquet with fresh bread in the round tower above.  The Knights Templar introduced woollen cloth fulling at the mill in the 13th century, explaining the continuous history of weaving traditions among the locals of Ardfinnan.  One such local named William le Teynturer (William the Dyer) is recorded in the village in 1295.  This was not the beginning of the mill, for a monastic centre had been established here since the 6th century by Saint Finnan, to whom Ardfinnan is named after.  It was here too that Saint Carthage took refuge and was granted the similar place of Lismore where he established his revered monastery and great centre of western learning.  Indeed one of the oldest watermills in the world was uncovered downstream, also in the Suir Valley, at Killoteran, dating to the 4th century.  The strategic crossing between Eastern and Southern Ireland being on the River Suir, it was one of the best trout and salmon fishing rivers in the British and Irish Kingdoms, naturally ideal for washing wool with its soft mountain water.