Presbyterians from the Irish province of Ulster were among the first to push the wild frontier west and found the city of Pittsburgh. By the 1840s, the flow of Irish Catholic immigrants had become a flood. Fleeing the great hunger and facing resentment in the city, they established themselves as key members of the community, building railroads and canals and establishing schools, hospitals and fraternal orders. During the Civil War, 156 women, many of them Irish, made the ultimate sacrifice for their new country when the Allegheny Arsenal exploded. The Fenians fought Southern Rebels under a green flag and made a little-known invasion of Canada in 1866. In the twentieth century, the sons and daughters of Erin took on roles as political leaders, labor agitators and entrepreneurs. Exploring tales of saints, sinners and visionaries, author Gerard F. O'Neil offers a beguiling and fascinating history of the Pittsburgh Irish.