Blessington was previously called Munfine, and in the Medieval period was part of the lordship of Threecastles. In 1667, Michael Boyle (the younger), Archbishop of Dublin and Lord Chancellor of Ireland, bought the lordship of Threecastles, previously the property of the Cheevers for £1,000. Boyle received a Royal Charter to establish the town of Blessington, in the townland of Munfine, as a borough.
Construction of Blessington House was begun in 1673 and afterwards St. Mary’s Church in Blessington, which was completed in 1683. On Boyle’s death in 1702 his son Murrough Boyle, 1st Viscount Blessington and Baron Boyle, inherited the Blessington estate. Murrough’s son, Charles, died in 1732 without an heir and the estate was inherited by his sister Anne, then her son William Stewart, 1st Earl of Blessington and Baron Stewart. Stewart died in 1769 without an heir and the estate passed to Charles Dunbar, a great grandson of Murrough Boyle, who also died heirless in 1778, when the estate passed to Wills Hill of Hillsborough, County Down, a great great grandson of Michael Boyle and the first Marquess of Downshire. The Hills held the estate until 1908.