Irish Patriot, United States Military Officer. He received notoriety for his military service in the American Civil War, serving in the Union Army as a cavalry officer, and for his stance for an independent Ireland from British rule. After immigrating with his mother and siblings from Ireland to New Jersey during the Irish Famine in 1848, he joined the United States Army in 1857. He served in the 2nd United States Dragoons during the Utah War, a military confrontation from May of 1857 to July of 1958 between the United States and the Utah Territory against the Mormon settlers entering Utah. He left the military, maybe in desertion, for California. At the dawn of the American Civil War, he re-entered the United States Army as a sergeant in the 1st Cavalry. In December of 1862, he received his commission as an officer in the 5th Indiana Cavalry. He was later transferred as a captain to the 17th United States Colored Infantry. Before the end of the war, he left the military with no further promotions and married Mary Crow. Although he fought in valor, he lacked a formal education, which may have impacted his military promotions. After the war, he settled in Tennessee, working as a claim's agent. He became part of the Fenian Brotherhood, a secret militant organization within the United States, working toward the Irish Republic. After gathering 600 to 800 Irishmen, mainly miners who had gained military experience during the American Civil War, he led the group to upper New York State. On June 1, 1866, O'Neill led a Fenian invasion of Canada with the goal of using occupied territory as a bargaining point with England for Irish's independence. In a 3-day invasion, he fought at Ridgway and Limestone Ridge, gaining a foothold in Canada. This was a military success but a political disaster. The invasion would ultimately fail to achieve their stated goals and upon returning to the United States, O'Neill was arrested by United States Marshalls charging him for violating the neutrality laws with Great Britain. Eventually, the charges were dropped after he promised not to do that again. He was pardoned by United States President Ulysses Grant. He was made president of the Fenian Brotherhood and given the rank of "General." Without the support of the Fenian Brotherhood, he and a group of followers entered Canada again at Manitoba on October 5, 1871, capturing a Hudson's Bay post. This time he was taken in custody by the United States Army. Once again, he was released after abandoning the Fenian Brotherhood. He did attempt to organize a third Canadian raid but failed. In an attempt to improve the living conditions of the Irish in the city slums in the eastern United States, he helped to form Irish communities in the vast lands of Nebraska. The most-noted community would come to be known as O'Neill, Nebraska. The rank "General" on his grave marker refers to his service in the Fenian Brotherhood, not to his United States military service.