The major impetus for the huge irish immigration to the united states after 1845 was:

The Irish Potato Famine, also recognized as the Great Hunger, commenced in 1845 when a fungus-like plant described as Phytophthora infestans circulated swiftly everywhere in Ireland. The infestation exhausted up to one-half of the potato crop and approximately three-quarters of the harvest over the subsequent seven years.

Before it finished in 1852, the Potato Famine occurred in the loss of approximately one million Irish from hunger and similar causes, and also forced millions of people to leave their motherland as foreigners.

theodore roosevelt 26th u.s. president : i admire his energy and passion. he was a fundamentally good man, brilliantly intelligent, possessed of extraordinary will and ability, supremely self-confident, bold, egalitarian, idealistic…. , lord, can we have him back?