The first major wave of Irish immigrants to America occurred in the 18th century. Many were Scots-Irish Presbyterians fleeing religious persecution in Ireland and settled in the Appalachian region. The larger wave of Irish Catholic immigration began in the mid-19th century due to the Great Famine (1845-1852), a devastating potato blight that caused mass starvation and forced millions to seek a new life in America. Upon arrival, these immigrants faced prejudice and discrimination due to their religion, poverty, and perceived lower social status.