Early Irish immigration was predominantly Presbyterian, and often gravitated to the frontiers of the time. The Great Famine (1848–52) triggered a massive increase in immigration, which was overwhelmingly Catholic. The newer arrivals usually settled in major urban centres, particularly New York, Boston and Philadelphia. The New England mill towns and major construction projects (railroads, canals) further west also attracted major influxes of Irish labour. By the early 1900s, Irish migrants dominated certain occupations: 80 per cent of the New York police force was of Irish descent, while Irish women constituted a large proportion of domestic servants, textile mill-workers, and, increasingly, teachers. While Irish immigration remained substantial after the turn of the century, the main countries of origin became southern and eastern Europe. The US Immigration Act (1891) introduced federal supervision of immigration, including the Ellis Island processing centre. Eventually the Immigration Acts of 1921 and 1924 imposed nationality-based quotas.
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