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...