Adjoined to the north-east shore of Lough Neagh, the county covers an area of 3,086 square kilometres (1,192 sq mi) and has a population of 651,321,[7] as of the 2021 census.

[9] The inland slope is gradual, but on the northern shore the range terminates in abrupt and almost perpendicular declivities, and here, consequently, some of the finest coast scenery in the world is found, widely differing, with its unbroken lines of cliffs, from the indented coast-line of the west.

The most remarkable cliffs are those formed of perpendicular basaltic columns, extending for many miles, and most strikingly displayed in Fair Head and the celebrated Giant's Causeway.

On both coasts there are several resort towns, including Portrush (with well-known golf links), Portballintrae and Ballycastle; on the east Cushendun, Cushendall and Waterfoot on Red Bay, Carnlough and Glenarm, Larne on the Sea of Moyle, and Whitehead on Belfast Lough.

The fisheries of the Bann and of Lough Neagh (especially for salmon and eels) are of value both commercially and to sportsmen, the small town of Toome, at the outflow of the river, being the centre.

A traditionally Protestant-majority county since the Plantation of Ulster by Scottish and English settlers, the 2021 census revealed that those of a Protestant and Other Christian community background were no longer a majority in Antrim, comprising 47.0% of the population,[17] a sharp decline from 75.2% in 1861.

The earliest known inhabitants were Mesolithic hunter-gatherers of pre-Celtic origin,[27] but the names of the townlands or subdivisions, supposed to have been made in the 13th century, are all of Celtic derivation.

A revival of Gaelic power followed the campaign of Edward Bruce in 1315, leaving Carrickfergus as the only significant English stronghold.

A branch of the O'Neills of Tirconnell (modern Tyrone) migrated to Clandeboye in the 14th century, and ruled it for a time from their castle on Lough Neagh.

During the Tudor era (16th century) numerous adventurers from Britain attempted to colonise the region; many Scots settled in Antrim around this time.

The Spanish vessel La Girona was wrecked off Lacana Point, Giant's Causeway in 1588 with the loss of nearly 1,300 lives.

Cary was part of the Glynnes; ruled originally by the O'Quinn sept, the MacDonnell galloglasses from Scotland took power here in the late Middle Ages and some of the O'Haras also migrated from Connaught.

Islandmagee had, besides antiquarian remains, a notoriety as a home of witchcraft, and during the Irish Rebellion of 1641 was the scene of an act of reprisal (for the massacre of Protestants) against the Catholic population by the Scottish Covenanter soldiery of Carrickfergus.

[10] In 1689 during the Williamite War in Ireland, County Antrim was a centre of Protestant resistance against the rule of the Catholic James II.

During the developing crisis James' garrison at Carrickfergus successfully repulsed an attempt by local Protestants to storm it.

After the advance of the Irish Army under Richard Hamilton, all of County Antrim was brought under Jacobite control.

Later in the year a major expedition from England under Marshal Schomberg landed in Belfast Lough and successfully laid siege to Carrickfergus.

The antiquities of the county consist of cairns, mounts or forts, remains of ecclesiastical and military structures, and round towers.

There are some remains of the ecclesiastic establishments at Bonamargy, where the earls of Antrim are buried, Kells, Glenarm, Glynn, Muckamore and Whiteabbey.

[10] The natural rock formations of Giant's Causeway on the Antrim coast are now designated a UNESCO World Heritage Site.

Slemish, about eight miles (13 km) east of Ballymena, is notable as being the scene of St Patrick's early life.

[10] According to tradition Saint Patrick was a slave for seven years, near the hill of Slemish, until he escaped back to Great Britain.

Records of the seaweeds of County Antrim were brought together and published in 1907 by J. Adams[37] who notes that the list contains 211 species.

Of the freshwater algae there are 10 taxa in the Charophyta (Charales) recorded from County Antrim: Chara aspera var.