Late 1600s--Scots-Irish Presbyterians from the north of Ireland begin to migrate to the North American colonies.

1770--Scots-Irish immigrants number about 80,000.

1775--Of the 2.5 million people in the colonies at the beginning of the American Revolution, about 250,000 were Scots-Irish.

1830s-1840s--Ireland suffers severe famines.

1840s-1920s--About 4.5 million Irish immigrants arrive in the United States.

1924--The Immigration Act of 1924 (the National Origins Act) assigned generous immigration quotas to Britain, Germany, and Ireland, whose citizens were deemed more likely to "fit in" with Americans than immigrants from southern and eastern Europe.