John Cusacke was a wealthy merchant, landowner and politician in seventeenth-century Dublin, who served as Mayor and Sheriff of Dublin. He was born in County Meath, eldest of the ten children of Patrick Cusacke of Ballymolghan and his wife Maud Plunkett, daughter of Thomas Plunkett of Lagore, Ratoath. He was admitted as a freeman of the city of Dublin in 1592, having served his apprenticeship. He married Margaret Allen, daughter of Giles Allen, a former Mayor of Dublin, and widow of John Gough, an alderman of Dublin. They had five children, including Robert, who inherited his father's estate and sat in the Irish House of Commons as MP for Kells in 1640-42, and Anne, who married Richard Barry. John served as Sheriff of Dublin City in 1599-1600 and was an alderman of Dublin Corporation from 1604 until his death. He was active on several committees of the Corporation, and served as Treasurer in 1610-11. He was Mayor of Dublin in 1608-9: Robert Kennedy, who had hoped for the position, was apparently passed over because he was a recusant. John, though he conformed outwardly to the Protestant faith, was far from unsympathetic to Roman Catholics, and was an active member of the Catholic Saint Anne's Guild, helping to protect its charter when it was under threat. He served four terms as one of the masters of the Dublin merchants' guild, and on their behalf he petitioned the English Crown in 1609 for repayment of loans owing to the Irish Treasury: he claimed that £1300 was owed to him personally, an indication of his considerable wealth. He became a substantial landowner in Dublin and Meath. The principal Cusacke family home was Rathgar Castle in what is now a suburb of Dublin, which he bought in 1609. All trace of it has vanished today, but it probably stood on present dayHighfield Road. He was the grandfather of two distinguished judges: Robert, his eldest son, was the father of Adam Cusack, justice of the Court of Common Pleas, and John's daughter Anne was the mother ofJames Barry, 1st Baron Barry of Santry, Lord Chief Justice of Ireland.