Focusing where possible on folk and early popular music as historical documents, this thesis investigates how successive waves of culturally alien Irish immigrants were able to overcome hostility and eventually integrate into the population of New York City. It establishes that legacies of Protestant reformation, British domination and Catholic deprivation carried from Ireland and Great Britain combined in New York City with economic and political competition to invigorate latent anti-Catholic and anti-Irish hostility. This process was greatly aggravated by the huge and incessant scope of immigration; and the unsuitability of a poorly-educated, rural people for settlement in an increasingly urbanised commercial industrial environment. Irish Catholics refused assimilation because it required the rejection of their heritage. Instead, they opted to integrate en masse through the acquisition of political power, a far longer process marked by ebbs and flows of fortune and opposition. Employing lyrics and the wider culture of folk and popular song, as well as period newspaper reportage and modern scholarship, the thesis traces the chronology of Catholic Irish integration beginning with the establishment of state and national sovereignty in late 1783. The Introduction provides broader thesis overview and definitions. Chapter One establishes that by 1700 official British colonial policy purposefully discouraged Catholic settlement in New York. Chapter Two shows conservative Federalist opposition to providing equal religious and political rights. Chapter Three examines the dual impact of Ireland's Great Hunger and America's Second Great Awakening. Chapter Four investigates the opportunity and challenge presented by the American Civil War, and the catastrophic Draft Riots of 1863. Chapter Five sees the Catholic Irish banish Orangeism, gain control of Tammany Hall and then the mayor's office. Throughout, songs illuminate the Catholic Irish path towards integration.