The experience of the Protestant minority in Ireland during the years of the Irish revolution has been the subject of much academic and popular debate in recent years. At issue is the extent to which the decline by one-third of the Protestant population of the Irish Free State between 1911 and 1926 was a result either of intimidation, sectarianism or ethnic cleansing during the revolution itself, or of more mundane factors such as long-term patterns of migration and low marriage and birth rates. Drawing upon digitised census returns and the rich detail contained in the records of the Church of Ireland, Presbyterian, and Methodist churches in County Longford, this article will show that the causes of depopulation are better understood when precise chronological, local, denominational and gender perspectives are brought to bear. It will argue for greater engagement with sociological literature to define more effectively the meaning of sectarianism in revolutionary Ireland. It will also invert the principal question of why the Protestants left and seek to explain why those who remained chose to do so. County Longford is chosen as a suitable case-study because it was affected by both long-term socio-economic factors and revolutionary violence, and the three Protestant denominations in the county have extensive archives which help to fill the gap in civil data occasioned by the absence of a census of population for fifteen years between 1911 and 1926. The article identifies dynamics present in Longford that can be explored in other regional contexts to achieve a wider national understanding of this demographic shift.