Answer:
Famine caused by a major crop failure
Step-by-step explanation:
Famine caused by a major crop failure was the primary reason for the migration of Irish immigrants to the United States between 1846 and 1855. This period is known as the Great Famine or the Irish Potato Famine, as the potato crop, which was a staple food for the Irish population, failed due to a fungus known as Phytophthora infestans. The famine resulted in mass starvation, disease, and death, as well as a significant decrease in the population of Ireland.