Until the middle of the eighteenth century the Antrim Estate extended all the way up the coast of County Antrim to Dunluce Castle, Ballycastle and beyond. Now, however, it is limited almost entirely to the land that sits within the walls of the Castle Demesne.

Today the Demesne, which was once a deer park, is a working estate consisting of forest, farmland and the Glenarm River. The Glenarm River is approximately 5 miles long, with the Glenarm Angling Club fishing two miles and a private syndicate fishing the remaining three miles.