Clonmore Castle is a twelfth century fortress but there was no mention of it until the 14th Century when it was repaired by Sir Anthony de Lucy in 1332. In the 15th Century it was one of several castles granted to the Earl of Ormond.

Typical of the late 13th century, the castle is nearly square in plan, with rectangular towers at the two southern corners, and smaller turrets at the other two corners. Remains of the main interior buildings can be seen on the eastern side of the courtyard. There are several interesting features remaining such as windows, stairway, chambers and narrow passages.

Clonmore was captured by the Earl of Kildare in 1516 and by the Earl of Ormond in 1598. It changed hands several times in the Confederate War, and was finally taken by Cromwell's forces under Colonel Hewson in 1650.

Clonmore Monastic Site

In the village graveyard, 300 yards to the east, there is one plain High Cross in the churchyard on the north side of the road, and considerable fragments of another, along with many slabs bearing a cross in relief, in the graveyard on the south side of the road. The road, cuts through the site of an old monastery founded by St. Mogue in the 6th century.