The Coollattin estate
Coolboy and the country around it were, for most of two centuries, part of the Coollattin estate - the Irish holding of the Fitzwilliam family, the Earls Fitzwilliam, whose seat was at Coollattin House a few kilometres south near Shillelagh. At its height the estate ran to roughly 88,000 acres, carried around twenty thousand tenants, and covered close to a quarter of County Wicklow. The early-nineteenth-century shape of the village - the regular cottages, the layout of the lanes - dates from that estate period. The Topographical Dictionary of 1837 recorded Coolboy, also then called Castleboy, as a village of 105 inhabitants on the road from Carnew to Rathdrum, holding eight fairs a year. It noted Coolboy House nearby, the residence of John Chamney. The golf course at Coollattin is laid out on the old demesne land.