The Drenagh estate, then known as Fruithill, was acquired from the Bishopric of Derry by
William Conolly (1662–1729), a wealthy
self-made man and speaker of the
Irish Parliament. By his will he left his interest in the property to his agent Robert McCausland “as an acknowledgment for the faithful service he has done me”, and the bequest allowed the McCauslands to establish themselves as county gentry. McCausland was the grandson of Baron Alexander McAuslane who had settled in the
Strabane area in the 1540s, and he named his first son (by his wife Hannah, née Moore) Conolly McCausland for his employer. In the 1730s Robert McCausland built the first house at Fruithill, located to the south-east of the present building, and in the 1790s this house was extended. Nothing remains of this house, though a walled garden remains from this period as well as elements of the demesne landscape. Conolly McCausland married the heiress Elizabeth Gage and had a son, also Conolly McCausland, who married Theodosia Mahon from
Strokestown, County Roscommon. This second Conolly McCausland approached architect
John Hargrave to design a new house, but only the gate lodge was built prior to the deaths of McCausland and Hargrave. On 4 March 1972, this same Captain Marcus McCausland, aged 39, a retired Catholic member of the
Ulster Defence Regiment, became the first UDR soldier murdered by the
Official Irish Republican Army (OIRA). He was shot dead by the Braehead Road in Derry. In 2014, the McCausland family were forced to place Drenagh on the market, but following the partial sale of the estate the family were able to retain ownership of Drenagh. On 5 May 1943 a
Royal Air Force Vickers Wellington (LB241) crashed on the estate grounds shortly after taking off from
RAF Limavady; all six crew died. ==Gardens==