First found in county Meath, where they held a family seat from very ancient times.

In the 18th and 19th centuries hundreds of thousands of Irish people immigrated to North American shores. The early settlers were enticed by the promise of their own land, but they were moderately well off in Ireland when they decided to emigrate. Therefore, they were merely carrying out a long and carefully thought out decision. The 1840s saw the emergence of a very different trend: thousands of extremely desperate people crammed into passenger boats hoping to find any type of opportunity. The Irish of this decade had seen their homeland severely stricken by crop failures which resulted in widespread disease and starvation. At whatever time the Irish immigrants came to North America, they were instrumental in the rapid development of the emerging nations of the United States and what would become known as Canada. An exhaustive search of passenger and immigration lists has revealed many persons bearing the name O'Regan, or one of its variants: John Regan, who settled with his wife and three children in Prescott, Ontario, Canada, in 1825; James, John, Patrick, Thomas and William O'Regan, who all arrived at Philadelphia between 1840 and 1860.

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