First found in Leinster where they held a family seat from ancient times.

The 19th century saw a great wave of Irish migrating out of their homeland in a great measure due to the oppressive imperial policies of the English government and landowners. Many of these Irish families sailed to North America aboard overcrowded passenger ships. By far, the largest influx of Irish immigrants to North America occured with Great Potato Famine during the late 1840s. These particular immigrants were instrumental in creation of the United States and Canada as major industrial nations because the many essential elements such as the roadways, canals, bridges, and railways required an enormous quantity of cheap labor, which these poor immigrants provided. Later generations of Irish in these countries also went on to make valuable contributions in such fields as the arts, commerce, politics, and education. Extensive research into immigration and passenger lists has revealed many early immigrants bearing the name Cosgriff: Anne Cosgrave, aged 34; Anne aged 12; Anne aged 18; Bridget aged 22; Bridget 50; Catherine, Ellen, Francis, Hannah, James, John, Julia, Margaret, Mary, Michael, Owen, Pat, Peter, Thomas, William Cosgrave, who all arrived in Quebec in 1848.

For more information on the last name Cosgriff, the PDF Surname History is available for purchase as well as other products.