It is popularly believed that Carrickfergus derived its name from a king called Fergus having been lost there in a storm about 320 B.C., whose body was washed up on the rocky peninsular where the castle stands. The name is, however, more likely to be a corruption of Carraig na Fairge, signifying “rock of the sea.” It is often erroneously called Knockfergus in ancient documents. The town is situated on the northern shore of Belfast Lough, about ten miles distant from that city.

The castle occupies the whole of a tongue of rock at the south end of the town, which was at one time surrounded on three sides by water.

The entrance to the fortress on the north, or landward direction, was by a drawbridge across a dry moat. This was protected by two semicircular towers, and a portcullis which still exists. Above the entrance is an aperture, from which missiles and lead could be poured upon besiegers.

From the gate towers a high curtain follows the formation of the rock that gradually rises to about 30 feet in height towards the south. The wall is at present mounted with ordnance used by the militia. The enclosed space is divided into two yards. The outer one, which is entered immediately from the gateway, contains a number of buildings and offices erected in 1802, at which time the castle was used as a barrack. There are also vaults, which were supposed to be bomb proof. In the line of wall is situated a small projecting tower known as the “Lion’s Den.” The inner yard is approached through a round arched gateway, and contains storehouses and keep. This latter is 90 feet high, and divided into five storeys. Its western side forms part of the outer wall. It was formerly entered by a doorway on the second floor, and a winding stone staircase in the wall of the west angle led to the top. Loopholes admitted light and air, and there was a small door at each storey. At present the ascent is made partly by wooden stairs inside. There are two towers at the summit of the keep, one on the south-east corner covering the top of the stairway, and the other at the south-west corner, which was intended for a sentry-box.

On the third storey is the large room known as “Fergus’s Dining-room,” being 40 feet long by 38 feet broad and over 25 feet high. It was made into a barrack in 1793, but is now employed as an armoury. Over the chimneypiece was once a stone inscribed in Irish, which was removed in 1793.

The former draw-well of the castle, 37 feet deep, was situated in the keep. It was famous for medicinal qualities. The lower portion of the building is now used as a magazine. The walls of the tower are 9 feet thick, and the corner stones, or quoins, are of yellowish limestone, which was probably quarried in the County Down on the opposite shore of the Lough.

The building of the castle is generally ascribed to John de Courcy, and, although there is no direct proof that this was the case, many facts tend to support the supposition. In the first place, as De Courcy settled a colony in Carrickfergus shortly after his conquest of Ulster, it is most likely that he would provide some means for its protection. Again, it was for a long time the hereditary property of the Earls of Ulster, who were descended from De Courcy. The ancient seal of the mayor of the town bears a spread-eagle, which was the De Courcy crest, and several coins of Henry II.’s time have been found near the building. In a preface to State Papers the editors say that “the oldest fort in Ulster is Carrickfergus, built in the days of De Courcy, and never out of the possession of the English.”

In 1605, the Lord Deputy applying for means to have it restored, remarks it was “founded by his Majesty’s ancestors, and much needing repair.”

It is likely King John stayed in the castle during his visit to Carrickfergus in 1210, and an order is preserved to the Bishop of Norwich to buy supplies for it that year. It appears to have passed into the hands of Hugh de Lacy when King John granted him Ulster, but in 1223 a garrison was to be placed in the castle lest it should be attacked by De Lacy, who was then plotting against the King.

The following year a band of knights and soldiers were despatched by the Earl of Pembroke for its further defence. Although it was being besieged by Hugh they managed to get into the fortress safely, and the siege was then raised.

Two years afterwards the custody of the castle was granted to Hugh de Lacy’s brother Walter.

In 1245 an order was issued for its repair, and later (1253) it was assigned by the King as part of the dowry of Eleanor, Queen Consort.

In 1315 the castle was besieged by Edward Bruce, and Lord Mandeville, who endeavoured to relieve it, failed to do so. The gallant little garrison held out for more than a year, and it is said they were reduced to eating eight Scotch prisoners who had died within the walls. Upon the arrival of King Robert Bruce to aid his brother, the fortress was surrendered. After the death of Edward Bruce the castle passed again into the hands of the English, and it appears to have been the only place in Antrim not in the possession of the O’Neills after the assassination of the Earl of Ulster, 1333.

In 1337 the King appointed a constable to the castle under the belief that he was the owner of the stronghold, instead of holding it only during the minority of the Earl of Ulster, and as there was a constable already in office, compensation had to be found for the disappointed custodian. From this time there was a long list of constables, the last being Stewart Banks, Esq., of Belfast, who used merely to attend annually to see the Mayor sworn in the outer yard of the castle. In 1461 an Act of Parliament decreed that none but Englishmen should hold the office of Governor. The position is now a mere sinecure.

In 1390, in an order for repair, the castle is described as being “totally destitute and desolate of defence,” and sixteen years later its state does not seem to have been much improved.

For the next two years it was kept for nothing by Sir James Whyte, who then (1408) petitioned the Crown to give him aid against the threatened attack of O’Donnell and his Scots.

After the order for English custodians, James, Earl of Douglas, was appointed Governor of Carrickfergus Castle in 1463.

At the beginning of the next century Clannaboy Niall, son of Con of Belfast, was prisoner in the castle on account of a row between his servants and some soldiers (1507). He exchanged his freedom for sixteen hostages, but no sooner was he liberated than he returned with his followers and took the castle and the Mayor, and rescued his pledges. In 1552 Sorley Boy MacDonnell surprised Carrickfergus and carried off Walter Floody, the constable of the castle. In consequence of these disturbances the Earl of Sussex marched to relieve the town in 1555. Two years later Hugh O’Neill Oge and some other prisoners in the castle escaped to join James M’Donnell. In 1559 the fortress was walled in and repaired. The building seems to have been much dilapidated in 1567, and upon Sir Henry Sidney coming north the following year, he had the keep roofed and restored. When the Earl of Essex arrived by sea in 1573, he reports that he discharged the ward of the castle, for it “doth not serve of any use, having in it very few rooms, and none of those covered, so as I have no apt place to employ her Majesty’s munition and other store but in wet vaults.”

From 1583 to 1598 Carrickfergus was the only town held by the Queen in the district, and in the latter year the castle was but poorly provisioned.

General Monroe, with four thousand Scotch auxiliaries, landed and took the castle in 1642, but four years later he was surprised by General Monk, who occupied the stronghold for the Parliament, being made Governor of it shortly afterwards.

The next year, but small resistance was offered to Lord Inchiquin, who then held it for the King for a few months, and it was retaken by Sir Charles Coote, who appointed a Governor for the Commonwealth.

In 1666, while the Duke of Ormond was at the head of affairs, so great was the dissatisfaction that the castle was seized by mutinous soldiers, and a strong force was required to quell the disturbance.

Eight years later the fortress was ordered to be furnished with twenty cannon.

The adherents of James II. sustained here a siege for six days from the troops of the Duke of Schomberg in 1689, after which they surrendered. It was on the 14th of June in this year that King William III. landed at Carrickfergus from the yacht Mary.

In 1711 50 feet of the outer wall fell down, and the tower was roofed with lead.

The castle was taken by the French Commodore ThurÔt with three ships of war in 1760, but his squadron was captured a few days later by the English fleet.

In 1797 the United Irishmen laid a plot to seize the castle, which was discovered by one of the garrison turning informer.

The year after the rebellion State prisoners were confined at Carrickfergus, having been sent from Belfast. At one time the fortress was used as a prison for all Antrim.

In 1814 a small square tower on the south side was taken down and rebuilt.

The castle is now in the possession of the Crown.