Ellis Island is located just of the coast of Manhattan, New York, and was where immigrants were traditionally registered before entering America. One such immigrant was Vito Andolini, who was mistakenly registered as 'Vito Corleone'. He was briefly contained here for having smallpox, before being taken in by the Abbandando family.
When Vito arrives on Ellis Island he is marked with an X inside a circle. In reality this meant he was suspected of having a mental health issue.