A sizeable ruined fortress on the Seagate in Irvine (North Ayrshire), Seagate Castle comprises a main block that still rises to three storeys and three projecting towers, although only two remain extant. The entrance is through a fine moulded semi-circular archway into a courtyard which once enclosed ancillary buildings. The ground floor of the main block includes a kitchen with large fireplace, a grand hall once occupied the floor above with private chambers above that. Other features which remain include guard-chambers, defending the entrance passage, a pit-prison and a watch-tower on top of one of the projecting towers, which overlooked the old Irvine Harbour.
There was probably a wooden tower on this site in the early 12th C., the property of the De Morville family, which was later rebuilt in stone. The Treaty of Irvine was signed here on 9th July 1297 which, for a time, brought peace between Scotland and England. Seagate Castle passed through the hands of the Balliols, Robert, High Steward of Scotland, and then to the Montgomeries of Eglinton around 1361. The present structure dates mostly from a reconstruction between 1562 and 1585 for Hugh Montgomerie, the 3rd Earl of Eglinton (c.1531-85). Stonework panels includes the arms of Montgomerie and of his wife Agnes Drummond of Innerpeffray, who he married in 1562. Mary, Queen of Scots (1542-87), stayed here as their guest in 1563.
The castle served for a time as a Dower House for Montgomeries and remained in use until 1746 when the roof was removed The property was presented to the Burgh of Irvine in 1945.
