The Great Hunger caused in Ireland from 1845 to 1852 is the Irish Potato Famine, a period of starvation & disease in the country. The period is also known as An Drochshaol or 'The Hard Times'.
About one million people died during and millions fled the country causing Irelands population to fall 20-25%.
The cause of the famine was Potato Blight that infected the crops throughout Europe during the 1840s a fungus called Phytophthora infestans caused by the rain & insects was spread rapidly throughout Ireland and Europe. This ruined up to one/half of the potato crop that year and three-quarters of the crop over the coming seven years.
The potato was the principal source of nutrition for the vast majority of citizens in Ireland mainly for the rural and poor as they were nutritious and had a plentiful harvest in the country, It became a staple diet in the 1800s and suited the Irish climate, by 1845 millions of the population in the country was dependent on Potato.
The population was dependent on a particular variety called Irish Lumper and this dependency put Ireland at risk of mass famine. Though one of the sources of the Blight was believed from the ships arriving through the United States as its first strain was seen in 1843 on America's Seaboard.
Due to the famine, the food in the cellars got rotten, the crops were destroyed and the deprivation became prominent. Causing around one million deaths from starvation and hunger-related diseases the other Million emigrated, thus the country lost a quarter of its population. Even in this situation, another major problem was that the food was still being exported to Great Britain as Ireland was under British rule at that time
The impact was felt alongside Europe and even the US as about two-third of the emigrants came to the country. The Irish refugees that reached the east coast of the USA established themselves in Boston, New York City, Philadelphia & Baltimore.
After the passage of the famine, the population in the country was reduced from 8.2 million to 6 million in 1851.
The Great Famine is regarded as one of the worst times in Irish History resulting in a century-long population decline. Today, the famine is remembered in the form of memorials in Ireland and the region of greatest losses also in immigrant cities such as New York for the migrants and people who died and suffered.