General John O'Neill, founder of O'Neill, was one of the most colorful leaders in the early development of Nebraska. Born in Ireland in 1834, he served as a U.S. Army officer from 1857 to 1864, then became active in the Fenians, an American organization promoting Irish independence. After leading several ill-fated raids against British military posts in Canada from 1866 to 1871, he lost his leading position in the movement, but in 1871 he did not give up the cause. As thousands of Irish left troubled Ireland for crowded American cities, O'Neill became interested in founding agrarian colonies in the West. He chose Holt County on Nebraska's frontier for his first colony. The first colonists arrived in May 1874, and his fourth and last group arrived in 1877. O'Neill died the following year, but the town was already the county seat and growing. Although Nebraska had numerous Irish settlements, O'Neill was the largest formal Irish colony, and its citizens have always been proud of their Old World heritage.