From 1848 - 1950 over 6 million adults and children emigrated from Ireland - over 2.5 million departed from Cobh, making it the single most important port of emigration. This exodus from Ireland was largely as a result of poverty, crop failures, the land system and a lack of opportunity. Irish emigration reached unprecedented proportions during the famine as people fled from hunger and disease.
Many famine emigrants went initially to British North America (now Canada) because of fare structures and government regulations, but the majority subsequently settled in the United States. The famine resulted as a consequence of widespread potato crop failure. Failure of the crop was not unusual in Ireland so the partial failures in 1845 did not cause particular concern. In 1846 the potato crop failed completely and in the years 1847-1849 there was either total or partial crop failure of whatever potato crop could be planted. Escape was seen by many as the only chance for survival : between 1845 and 1851 over 1,500,000 people emigrated from Ireland This was more than had left the country in the previous half century.
Source: Cobh Heritage Center