Mitchel is the son of a Presbyterian minister. At the age of four, he is sent to a classical school, run by an old minister named Moor, nicknamed “Gospel Moor” by the students. He reads books from a very early age. When a little over five years old, he is introduced to Latin grammar by his teacher and makes quick progress. In 1830, not yet 15 years old, he enters Trinity College, Dublin and obtains a law degree in 1834.
In the spring of 1836 Mitchel meets Jane Verner, the only daughter of Captain James Verner. Though both families are opposed to the relationship, they become engaged in the autumn and are married on February 3, 1837 by the Rev. David Babington in Drumcree Church, the parish church of Drumcree.
Mitchel works in a law office in Banbridge, County Down, where he eventually comes into conflict with the local Orange Order. He meets Thomas Davis and Charles Gavan Duffy during visits to Dublin. He joins the Young Ireland movement and begins to write for The Nation. Deeply affected by the misery and death caused by the Great Famine, he becomes convinced that nothing will ever come of the constitutional efforts to gain Irish freedom. He then forms his own paper, United Irishmen, to advocate passive resistance by Ireland’s starving masses.
In May 1848, the British tire of Mitchel’s open defiance. Ever the legal innovators in Ireland, they invent a crime especially for the Young Irelanders – felony-treason. They arrest him for violating this new law and close down his paper. A rigged jury convicts him, and he is deported first to Bermuda and then to Australia. However, in June 1853, he escapes to the United States.
Mitchel works as a journalist in New York City and then moves to the South. When the American Civil War erupts, he is a strong supporter of the Southern cause, seeing parallels with the position of the Irish. His family fully backs his commitment to the Southern cause. He loses two sons in the war, one at the Battle of Gettysburg in 1863 and another at the Battle of Fort Sumter in 1864, and another son loses an arm. His outspoken support of the Confederacy causes him to be jailed for a time at Fort Monroe, where one of his fellow prisoners is Confederate President Jefferson Davis.
In 1874, the British allow Mitchel to return to Ireland and in 1875 he is elected in a by-election to be a member of the Parliament of the United Kingdom representing the Tipperary constituency. However his election is invalidated on the grounds that he is a convicted felon. He contests the seat again in the resulting by-election and is again elected, this time with an increased vote.
Unfortunately, Mitchel, one of the staunchest enemies to English rule of Ireland in history, dies in Newry on March 20, 1875, and is buried there. Thirty-eight years later, his grandson, John Purroy Mitchel, is elected Mayor of New York City.