17 March 1846,
The first refugee boat left the port of Dublin during the Great Hambruna in Ireland. Potato production, which was part of the basic diet for two-thirds of the Irish, suffered a deficit due to an epidemic. Population impoverishment and tensions between owners and tenants increased. There were several riots resulting in one million deaths and so many refugees. Irish Republicanism was a great boost, due to British mismanagement and the deterioration of the living conditions of Catholics.
Source:
Christine Kinealy, The Great Irish Famine. Impact, Ideology and Rebellion (Palgrave).