Early writers tell how an island off Skerries was used as a landing place for an invasion, which happened in the second century. This island was either Shenick or Red Island, which would have been a tidal island at the time. When the invaders landed, they formed ranks and at low tide marched to the mainland, where they were promptly defeated at the ancient settlement of Knocknagin, north of Balbriggan. The islands were previously known as the Islands of Cor possibly after the original inhabitants.
As noted, in 432 AD, St. Patrick is reputed to have landed on Church Island, and according to the Annals of Inisfallen Saint Mochonna founded a monastery shortly afterwards.
In the year 797 AD, the Danes carried out one of their earliest raids in Ireland when they plundered the monastery on Church Island. As the origin of the name is Norse and many localities have Norse-based names, it is safe to assume the Vikings did settle and occupy the area. Sitric, who was a son of a Dane called Murchard, re-founded the monastery on Church Island in 1120. He dedicated it to St. Patrick, the Apostle of Ireland. By this time the Danes who had settled in Ireland had become Christians.
In 1148 Saint Malachy, Archbishop of Armagh, arranged a synod on St. Patrick’s island to settle differences between the Irish Christians and the Pope. Fifteen bishops, two hundred priests and other clergy were present.
In 1496 the King gave permission to the Prior of Holmpatrick to build a pier. At this time Skerries was the property of the monastery of Holmpatrick and was known as the Port of Holmpatrick.
In 1565, after the Reformation, the monastery and its lands became the property of Thomas Fitzpatrick. In 1605 the manor and lands of Holmpatrick was granted to the Earl of Thomand. In 1721 the last Earl sold the manor and lands, including the town of Skerries, to the Hamilton family of Hacketstown.
In 1897 the Hamilton family were granted the title of Lord Holmpatrick. Comparisons between maps of Skerries drawn in 1703 and 1760 suggest that the Hamilton family was responsible for setting out the streets of the town as they are today. Between 1863 and 1865 a monument to the memory of James Hans Hamilton, the local landlord and MP, was erected in Skerries. The Monument is a reduced scale replica of the Wellington Monument in the Phoenix Park, Dublin. It is now at the heart of the commercial centre of the town.
After the 1916 rising, a British Destroyer landed troops at Skerries to help the Dublin garrisons suppress the rising. 200 men of the North Staffordshire Regiment landed under the command of Captain Clay. To try and impede their progress to Dublin, local rebels blew up the bridge over the railway in Donabate.