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

North America accepted thousands of Irish immigrants during the 19th century as their homeland suffered under foreign imperialistic rule. Although settlers from the early portion of the century came to North America by choice in search of land, by far the largest influx of Irish immigrants came to North America during the Great Potato Famine of the late 1840s. Many of these Irish Families left the country destitute and in some cases suffering from disease. However, those who survived the long ocean voyage were especially vital to the development of industry in the United States and what would become known as Canada. Research of immigration and passenger lists has shown many early immigrants bearing the name O'Leary: Daniel, Denis, George, Jeremiah, John, Michael, Patrick, Thomas and William Leary, who all arrived in Philadelphia between 1840 and 1860; other Learys arrived in the ports of Boston, New York, San Francisco, Quebec..

Motto Translated: Strong is the King of the sea.

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