Newcastle takes its name from the castle, built by the Normans on an earlier Irish fortification in the territory of the O'Byrne's.

The castle, called Newcastle Mackynegan, became a major stronghold in the outer fortifications of the Pale.

The church is located a few hundred feet from the castle and some parts of the building date from the 12th Century.

[3] In 1872 the Archdeacon of Glendalough ceased to have a place in the Chapter, as such, and the separate prebend of Newcastle was revived.

Close by is Blackditch Wood,[4] an 89-hectare (220 acre) priority woodland and wetland Nature Reserve established by Birdwatch Ireland in 2002 and classified as a special protection area.

The project created a large wetland complex for the protection of Annex 1 birds threatened within the European Union.

The reserve comprises a variety of habitats, including pure birch forest, fen and willow scrub, natural grasslands, a conifer plantation, 8 km (5.0 mi) of drainage ditches and farmland for grazing and crop planting, attracting a wildlife diversity, protecting threatened bird, flora and insect species.