Before the middle-ages McCartan Country included the Baronies of Kinelarty, Dufferin and about one quarter of Castlereagh – all in the County of Down. Parts of another adjoining barony, that of  Iveagh, also came under their control for short periods. 
During the sixteenth century sections of these lands were lost to the colonists.  In 1600 the McCartans were still fairly strong and in control of mid Down, with strongholds at Magheraknock, Ballynahinch, Magheratimpany, Loughinisland, Drumnacoyle, Drumaroad, Finnebrogue and Ardilea.   Defeat of the Irish at Kinsale in 1601 greatly weakened the influence of Gaelic septs throughout the entire island. The McCartan stronghold of Kinelarty  became conspicuously vulnerable.  Government agents reported the McCartans still practised  the ancient Irish custom of tanistry.  In 1605 the McCartans were pressurised into parting with one third of their lands to Lord Edward Cromwell, Earl of Ardglass. 
In 1642 the remainder of Kinelarty, comprising of the parishes of Magherahamlet, Magheradroll and Loughinisland was confiscated when Patrick and Owen McCartan, leaders of their name, were jailed in Carrickfergus for playing a prominent role in the insurrection. 
After the 1680's, with the strengthening influence of the Jacobites, hope of a native Irish land restoration was raised.  The defeat of James II by William III at the Boyne in 1690 dashed this possibility and marked the end of  McCartan influence in mid Down.  Many of their able bodied were amongst the 40,000 Irishmen, known as 'The Wild Geese', who departed to join the armies of France, Spain and Austria.