As of 1880 more than 5 million Irish and Irish Americans resided in the United States.

Daniels takes us behind these numbers:

But if we look behind the numbers, other significant differences appear in the new pattern of Irish immigration. Much of the very early migration had been heavily male; in the famine decades, migration was largely a family affair, although to be sure, many families arrived serially in chain migration and others were mutilated by the high mortality of those years. Males still predominated, but not by a very large margin. In the post-famine years, and particularly after 1880, more females came from Ireland than males. The best data on Irish emigration compiled by Kerby Miller, show this very clearly. From 1851 to 1880, males outnumbered females among Irish emigrants to all destinations by a ratio of 1.14 to 1. From 1880 to 1910 the ratio is 0.98 to 1, showing a slight female preponderance. Similarly, Archdeacon's chart of ethnic "maleness" shows Irish-born Americans as the only group with a female majority, 53.6 percent.

The reasons for this are to be found in Ireland, not America. While the position of women in Irish society was always quite disadvantaged, their place in postfamine Irish society clearly worsened. The decline of cottage industry lessened their economic contribution and independence while the development of arranged marriages and an increasingly important dowry system made marriage more and more difficult. Ireland had the highest age of marriage in Europe, and about a quarter of Irishwomen who stayed home never married. Before the famine about 20 percent of all Irish wives were at least ten years younger than their husbands; by the early years of this century about half were. And in Ireland in contrast to Irishwomen who migrated to England or America women did not live longer than men. All of this made the emigration of women particularly young, single women a salient characteristic of Irish postfamine emigration, and one that grew more pronounced with the passage of time. One early immigrant, Mary Brown from County Wexford, writing from New York just before the Civil War, advised a friend to come over to a land "where thers love and liberty." To be sure, the life of immigrant women was filled with hard work at menial occupations, but compared to conditions in Ireland the fact that "good girls to do house work in respectable families can readily get from one and a half to two dollars per week and good board and food" made such work seem quite attractive, especially at first.