This dissertation examines the arc of Irish-Catholic identity in Griffintown, a working-class neighbourhood of Montreal, over the course of the "long" twentieth century, from 1868 to 2009. Griffintown is significant as it was both the first and last Irish-Catholic neighbourhood of the city. Situating the working-class Irish-Catholics of Griffintown within a postcolonial framework, this dissertation examines the development and functioning of a diasporic Irish culture in Montréal. We see how that culture operated in Griffintown, at times shielding the residents of the neighbourhood from goings on in the wider city and nation, and at other times allowing for the forging of common cause across class lines within the Irish-Catholic community of Montréal. In the years following World War II, Irish-Catholic Griffintown disappeared from the landscape, owing to depopulation and the physical destruction of the neighbourhood. We then see how Irish-Catholic identity in Montréal as a whole broke down, as the Irish made common cause with the Anglo-Protestants of the city to forge a new alliance: Anglo-Montréal. Thus situated, the Anglophone population of the city girded itself in a defensive posture for the linguistic, cultural, economic, and constitutional strife that dominated life in Montréal over the second half of the twentieth century. In the years since the second referendum on Quebec sovereignty in 1995, Irish identity has undergone a renaissance of sorts in Montréal, due to both developments locally and the reinvigoration of the Irish diaspora globally since the 1980s. In this process, we see the intersection of history and memory as Griffintown has become the site of Irish memory and remembrance on Montréal's cultural landscape. The Irish of Montréal, then, have used Griffintown as a means of claiming their space on the cultural landscape of the city and to demonstrate their long-standing connection to Montréal. In effect, Griffintown has allowed the Irish in Montréal to re-claim their stake as one of Montréal's "founding nations.