Hamilton Rowan is born in the home of his grandfather, William Rowan, in London on May 1, 1751 and lives there with his mother and sister for much of his early life. He is admitted to Queens’ College, Cambridge in 1768, but is expelled from the college and rusticated for an attempt to throw a tutor into the River Cam. He is sent for a period in 1769 to Warrington Academy.
Hamilton Rowan travels throughout the 1770s and 1780s, visiting parts of Europe, the Americas, and North Africa. In 1781 he marries Sarah Dawson in Paris, France. The couple has ten children. He is the godfather of the Irish mathematician William Rowan Hamilton.
Hamilton Rowan returns to Ireland in his thirties, in 1784, to live at Rathcoffey near Clane in County Kildare. He becomes a celebrity and, despite his wealth and privilege, a strong advocate for Irish liberty. That same year he joins the Killyleagh Volunteers, a militia group later associated with radical reform. He first gains public attention by championing the cause of fourteen-year-old Mary Neal in 1788. Neal had been lured into a Dublin brothel and then assaulted by Lord Carhampton. Hamilton Rowan publicly denounces Carhampton and publishes a pamphlet A Brief Investigation of the Sufferings of John, Anne, and Mary Neal in the same year. An imposing figure at more than six feet tall, his notoriety grows when he enters a Dublin dining club threatening several of Mary Neal’s detractors, with his massive Newfoundland at his side and a shillelagh in hand. The incident wins him public applause and celebrity as a champion of the poor.
In 1790 Hamilton Rowan joins the Northern Whig Club, and by October has become a founding member of the Dublin Society of United Irishmen, working alongside famous radicals such as William Drennan and Theobald Wolfe Tone. He is arrested in 1792 for seditious libel when caught handing out “An Address to the Volunteers of Ireland,” a piece of United Irish propaganda. Unknown to him, from 1791 Dublin Castle has a spy in the Dublin Society, Thomas Collins, whose activity is never discovered. From February 1793 Britain and Ireland join the War of the First Coalition against France, and the United Irish movement is outlawed in 1794.
Hamilton Rowan’s reputation for radicalism and bluster grow during this time when he leaves Ireland to confront the Lord Advocate of Scotland about negative comments made in respect to his character and that of members of the Society of United Irishmen. As a prominent member of the Irish gentry, he is an important figure in the United Irishmen and becomes the contact for the Scottish radical societies as a result of his visit. Upon his return to Dublin, he is charged and was found guilty of seditious libel, even though he is excellently defended by the famous John Philpot Curran. He is sentenced to two years imprisonment, receives a fine of £500, and is forced to pay two assurities for good behaviour of £1,000 each. In January 1794 he retires to his apartments in Dublin’s Newgate Prison.
In the years following, Hamilton Rowan spends time in exile in France, the United States and Germany. He is allowed to return to Ireland in 1806. He returns to the ancestral home of Killyleagh Castle, County Down, receiving a hero’s welcome. While he has agreed to be a model citizen under the conditions of his return to Ireland, he remains active in politics and retains his youthful radicalism. Following his last public appearance at a meeting in the Rotunda in Dublin on January 20, 1829, he is lifted up by a mob and paraded through the streets.
Hamilton Rowan dies at the age of 84 in his home on November 1, 1834. He is buried in the vaults of St. Mary’s Church, Dublin.