To assert at the outset of this study, as I do, that the task before me is both impossible and essential, may be justly proclaimed a proceeding both cowardly and obvious. We are principally concerned with the nineteenth century, but the twentieth century prolonged many of the features of Irish Roman Catholic clerical identity of the nineteenth, in North America as elsewhere. Vitally important patterns and castes (social and mental) were established in the eighteenth century, and the first Irish-American Roman Catholic priestof major significance in the United States, John Carroll (1735-1815), first Roman Catholic bishop in the U.SA and first archbishop of Baltimore, owed his American birth initially to migration of his father’s kinsmen in the late seventeenth century. Anglophone North America from 178 3 consisted of two political obediences, with similarities and contrasts both subtle and, at least superficially, forceful. The huge and consistently expanding area of white settlement in North America in which the Irish Catholic clergy participated, created other great divergences: when American historians at the end of the nineteenth century under the influence of figures as divergent as Frederick Jackson Turner of the ‘frontier thesis’, Ulrich Bonnell Phillips of slavery apologetics, and Alfred Thayer Mahan of sea-power celebration, looked to environmentalism as the chief explanation of the American past, they may have oversimplified—indeed, they did oversimplify—but their sheer preoccupation with the question gives its own warnings against a filio-pietism which chooses to see an Irish ethnic character resolutely asserting itself to the third, fourth, and even later generations.