On a small piece of land, a farmer could grow enough potatoes a day, with some milk or cheese, and be very healthy. Soon, potatoes became the main food in Ireland. Then, in 1845, a disease killed all the potatoes in Ireland. Two million people died of hunger. Many Irish who did not die came to the United Stages at this time. Over a million Irish came to America; one of them was the great-grandfather of John F. Kennedy.