Irish immigrants first began arriving in Boston in the 18th century, driven away from their homeland by harsh political and economic conditions. Immigration increased dramatically with the Potato Famine in the mid-19th century, and the Irish became the largest immigrant group in Boston, developing a strong presence in South Boston in particular. Faced with xenophobic attitudes from those who saw the waves of Irish newcomers as invaders, the Irish American residents of Boston went on to show firm support for the Union during the American Civil War and, largely due to the highly visible efforts of such groups as the 9th Regiment Massachusetts Volunteer Infantry (known as the “Fighting Ninth”), gained distinction during the war. As historians now note, “Irish support for the Union helped to soften nativist sentiment against them while the war itself provided new opportunities for economic and social advancement” (“The Irish Atlantic: A Story of Famine, Migration, and Opportunity Open at the Massachusetts Historical Society.” MHS News. Massachusetts Historical Society, 10 Mar. 2017). 

As time went on, the Irish American residents of Boston gained greater political clout and representation in government. In 1884, Hugh O’Brien was elected the first Irish-born Roman Catholic mayor of Boston.