The Irish Potato Famine was the primary cause for this migration. Potatoes and other crops suddenly began to fail by an unknown cause (later known to be a fungus). Many Irish starved to death, and the English, who controlled the country at the time, took whatever food was not spoiled. Because of this, and because the United States was seen as a land of opportunity, millions of Irish crowded the ships westward bound in order to go to the United States.
