Thomas Francis Meagher, Irish nationalist and leader of the Young Irelanders in the Rebellion of 1848, drowns on July 1, 1867, after falling overboard from the steamboat G. A. Thompson into the Missouri River.

Meagher is born on August 3, 1823, at Waterford, County Waterford, in what is now the Granville Hotel on the Quay. He is educated at Roman Catholic boarding schools. When he is eleven, his family sends him to the Jesuits at Clongowes Wood College in County Kildare. It is at Clongowes that he develops his skill of oratory, becoming at age 15 the youngest medalist of the Debating Society. After six years, he leaves Ireland for the first time, to study in Lancashire, England, at Stonyhurst College, also a Jesuit institution. He returns to Ireland in 1843, with undecided plans for a career in the Austrian army, a tradition among a number of Irish families.

Meagher becomes a member of the Young Ireland Party in 1845 and in 1847 is one of the founders of the Irish Confederation, dedicated to Irish independence. In 1848 he is involved, along with William Smith O’Brien, in an abortive attempt to mount an insurrection against English rule. Arrested for high treason, he is condemned to death, but his sentence is commuted to life imprisonment in Van Diemen’s Land, now Tasmania.

Meagher escapes in 1852 and makes his way to the United States. After a speaking tour of U.S. cities, he settles in New York City, studies law, and is admitted to the bar in 1855. He soon becomes a leader of the Irish in New York and, from 1856, edits the Irish News.

At the outbreak of the American Civil War, Meagher becomes a captain of New York volunteers and fights at the First Battle of Bull Run in July 1861. He then organizes the Irish Brigade, and in February 1862 is elevated to the rank of brigadier general. After his brigade is decimated at the Battle of Chancellorsville in May 1863, he resigns his commission, however in December he returns to command the military district of Etowah, with headquarters at Chattanooga, Tennessee.

At the close of the war, Meagher is appointed secretary of Montana Territory where, in the absence of a territorial governor, he serves as acting governor.

In the summer of 1867, Meagher travels to Fort Benton, Montana, to receive a shipment of guns and ammunition sent by General William Tecumseh Sherman for use by the Montana Militia. On the way to Fort Benton, the Missouri River terminus for steamboat travel, he falls ill and stops for six days to recuperate. When he reaches Fort Benton, he is reportedly still ill.

Sometime in the early evening of July 1, 1867, Meagher falls overboard from the steamboat G. A. Thompson, into the Missouri River. His body is never recovered. Some believe his death to be suspicious and many theories circulate about his death. Early theories included a claim that he was murdered by a Confederate soldier from the war, or by Native Americans. In 1913 a man claims to have carried out the murder of Meagher for the price of $8,000, but then recants. In the same vein, American journalist and novelist Timothy Egan, who publishes a biography of Meagher in 2016, claims Meagher may have been murdered by Montana political enemies or powerful and still active vigilantes. On the frontier men are quick to kill rather than adjudicate. A similar theory shown on Death Valley Days (1960) has him survive the assassination attempt because his aide had been mistakenly murdered when he accepted one of his trademark cigars, and Meagher uses his apparent death as leverage over his political opponents.