In 1845 a disease called 'potato blight' ruined potato crops all over Ireland. Many people died from hunger because they had no other food to eat. This is known as the Great Irish Famine. It lasted for almost five years.
Many people had to leave Ireland in search of a better life. They went to places like America and England.
After the Famine the population of Ireland was much smaller. Less people farmed the land. Those who continued farming had larger farms. They grew crops and reared animals.
The people who were farming after the famine tried not to depend on the potato alone for their food. However, there were still some potato failures later on which caused suffering for the poorer farmers.