Cairncastle Presbyterian Church traces its founding congregation to 1646, just four years after the establishment of the Presbytery of Carrickfergus, the oldest Presbytery in Ireland. That makes it one of the very oldest Presbyterian congregations on the island. Down the road, St Patrick's Church of Ireland appears in the papal taxation of 1306 under the name Karkastell, which means the village already had a church here when Edward I was still grinding his way through the conquest of Scotland. The present St Patrick's was built in 1815, repaired and remodelled through the 19th century, and given an octagonal spire that was rebuilt in 1960. A brass plate on the font records that Dean Jonathan Swift, author of Gulliver's Travels, used it during his incumbency of Ballynure Parish in 1695.

The most-photographed object in the churchyard is not a headstone. It is a Spanish sweet chestnut tree, locally known as the Armada Tree. The legend, as locals tell it, runs like this: in 1588, when the wrecked galleons of the Spanish Armada were being driven onto the coasts of Ireland and Scotland by Atlantic gales, the body of one Spanish sailor washed up on the shore at nearby Ballygally. Carncastle people found him, buried him at St Patrick's in an unmarked grave, and forgot about him. Some time later, a chestnut sapling pushed up out of the earth above the grave. The story is that the sailor had been carrying chestnuts in his pocket, possibly to ward off scurvy, and one of them rooted and grew. Whatever the truth, the tree is real, the grave is supposed to lie beneath it, and a Spanish sailor most likely has six centuries of Ulster rain falling on a borrowed plot beside him.

About a mile west of the village rises Knockdhu, a Bronze Age promontory fort on a basalt escarpment. Three concentric banks and ditches enclose the remains of roundhouses and what archaeologists believe was a gatehouse, all set on a defensible ridge with a view that takes in the sea, the glens, and most of the surrounding country. The site sat largely undisturbed for three thousand years until 2008, when the Channel 4 archaeology programme Time Team arrived to excavate it, broadcasting their results in an episode that aired on 18 January 2009. The find pushed Knockdhu into the small front rank of Irish Bronze Age sites and gave the village a moment of national attention it had not seen since the Armada Tree.

The 21st century brought a more unexpected kind of fame. In 2010, HBO's Game of Thrones used the moorland above Carncastle - Knock Dhu, the same basalt outcrop crowned by the Bronze Age fort - as the location where Ned Stark, played by Sean Bean, executed Will, the deserter from the Night's Watch, in the first episode of the first season. It became one of the most viewed scenes in television. The wind that whips across that ridge, the dark grass, the great open sweep down toward the sea: all of it ended up on screens in every country where the show aired, beamed out from a hill that almost nobody outside North Antrim had ever heard of.

The Cairncastle Flute Band is one of the oldest Protestant marching bands in Northern Ireland, formed somewhere in the late 1850s and still going. They practise in the village but draw most of their members from nearby Larne. On parade days, the high steady tone of fifes carries across the village and out over the basalt ridge where the Bronze Age fort still keeps its silent watch. Carncastle is a small place with deep memory. The numbers on the census tell only the most ordinary version of its story.