Thomas Sweeny was born on December 25, 1820, at Cork, Ireland; he immigrated to the United States in the early 1830s. In 1846, he enlisted as a second lieutenant in the New York Volunteers and fought in the Mexican-American War. Sweeny was severely wounded at the 1847 Battle of Churubusco, requiring the amputation of his right arm. He received a commission in the Regular Army in 1848.

At the start of the Civil War, Sweeny helped defend the St. Louis Arsenal against pro-secessionist elements and assisted Captain Nathaniel Lyon in the capture of the Missouri militia at Camp Jackson. He accompanied Lyon to southwest Missouri and participated in the Battle of Wilson’s Creek.

Sweeny went on to command a brigade at Shiloh and Corinth and was promoted to brigadier general of volunteers in late 1862. He led a division during the Atlanta Campaign, but engaged in a brawl with two other officers following the July 22nd Battle of Atlanta, for which he was court-martialed. Acquitted, Sweeny commanded the Irish-American “Fenian” army during its failed invasion of Canada in 1866.

Thomas Sweeny retired from the army in 1870 as a brigadier general; he died on April 10, 1892.

Carte-de-Visite by Charles D. Fredericks, New York, N.Y.

Image Courtesy Wilson’s Creek National Battlefield; WICR 31496