Potato Famine (1845-1852): A devastating famine in Ireland due to potato crop failure; led to mass starvation and emigration, with many Irish Catholics immigrating to America.
Know Nothing Party: An American nativist political party that operated nationally in the mid-1850s primarily anti-Catholic and hostile towards immigration.
Tammany Hall: A New York City political organization founded in 1786 and incorporated on May 12, 1789 as the Tammany Society. It was dominated by Irish-Americans and became known for corruption and for helping immigrants (most notably the Irish) rise up in American politics.