"In 1845, a fungus began to destroy Ireland's potato crop, triggering a famine that would kill one million Irish men, women, and children--and drive over one million more to flee for America. Ten years later, the United States had been transformed by this stupendous migration, nowhere more than New York: by 1855, roughly a third of all adults living in Manhattan were immigrants who had escaped the hunger in Ireland. These so-called "Famine Irish"...