Approximately 40 million citizens of the United States claim Irish heritage. What is the story behind this astounding number? In the early years of the nineteenth century, Protestants - many of whom were skilled tradesmen - continued to account for the majority of Irish immigrants. By the 1820s and 1830s the overwhelming majority of those fleeing Ireland were unskilled Catholic peasants. One of the driving forces of emigration at this time was the fact that Ireland was becoming Europe's most densely populated country and the land could not support it. In addition, the increase in industrialization had diminished the need for weaving and spinning that had helped to supplement the income of some families. Most of the Irish Catholic immigrants during the eighteenth century became engaged in some sort of farming occupation; those in the subsequent century tended to remain in urban or textile towns. Many found jobs building roads or canals such as the Erie. Irish Catholic immigrants frequently found themselves a minority and targets of discrimination in an overwhelmingly Protestant nation. It was the Potato Famine of 1845-1851 that initiated the largest departure of Irish immigrants to the United States. Approximately 1.5 million people died of starvation and the epidemics that accompanied the famine. Many survivors immigrated to the United States. It has been estimated that, from 1820 to 1900, about four million Irish immigrated to the United States. The Irish peoples’ prowess and patriotism during the Civil War helped minimize previous discrimination. The increase of even poorer southern and eastern European immigrants also helped the Irish gain more status. By the end of the century, a high proportion was skilled or semi-skilled laborers or had trades. After World War I, Irish immigration to the United States was high, but declined when rules around immigration became stricter in the 1920s. Post-World War II numbers again increased; but the 1960s saw emigration from Ireland falling due to quota laws restricting northern Europeans. Emigration from Ireland continues, but some of it is illegal – 50,000 illegal Irish immigrants are estimated to be living in the United States.