Since the 18th century, around four million people have immigrated from Ireland to New York City. At one point, around half of all the city's residents were Irish, giving it a larger Irish population than any other city in the world. The housing these immigrants lived in was shabby, the jobs they worked were awful, and mainstream American society wasn't particularly fond of them. Fast forward 150 years, and the descendants of these impoverished famine refugees mostly live comfortable lives in the suburbs and are more or less indistinguishable from any other white Americans. In this four-part series, we'll take a look at how and why the Irish came to NYC in such huge numbers, what this journey was like, and how it permanatly changed the course of New York City's history.