Excerpts from Books and Wikipedia
"The legacy of the Great Famine in Ireland (…) followed a catastrophic period of Irish history between 1845 and 1852 during which time the population of Ireland was reduced by 20 to 25 percent. The famine was a watershed in the history of Ireland. Its effects permanently changed the island's demographic, political and cultural landscape. For both the native Irish and those in the resulting diaspora, the famine entered folk memory and became a rallying point for various nationalist movements. Modern historians regard it as a dividing line in the Irish historical narrative, referring to the preceding period of Irish history as "pre-Famine." [Wikipedia] "In 1845, the blight stole about a third of the potato crop, causing serious economic hardship; in 1846, virtually the entire crop was destroyed, and famine stalked the land. . . . In the decade 1846-55, over a million Irish people, perhaps a million and a half, died of starvation or diseases provoked by malnutrition such as cholera, typhus, dysentery, and typhoid fever. About two million emigrated to Britain, North America, or the Antipodes, with over half of them going to the United States." [Howe: What Hath God Wrought, p. 822-3]