Ferns is believed to have been established in the 6th century, when a monastery was founded in 598 dedicated to St Mogue of Clonmore who was a Bishop of Ferns.[6] The town became the capital of the Kingdom of Leinster when the kings of that southern part of the province established their seat of power there. King Dermot MacMurrough founded St. Mary's Abbey as house of Augustinian canons c. 1158 and was buried there in 1171.[7]
Ferns Castle, an Anglo-Norman fortress, was built in the 13th century by William, Earl Marshall. Today about half of the castle still stands. The town also contains the 13th-century St Edan's Cathedral (Church of Ireland) and several high crosses and parts of crosses.
