Ellis Island was an island in New York City. A major United States immigration hall was situated upon it.
In 1892, Jack Harkness got into a fight at the immigration centre, whereupon a man shot him though the heart. This caused his second death and proved to him he could not die. (TV: Utopia)
Jack passed through Ellis Island again in 1927, where he met Angelo Colasanto. (TV: Immortal Sins)
In 1966, the disused Ellis Island and other New York City landmarks were observed by the First Doctor, Ian Chesterton, Barbara Wright, and Vicki Pallister, whilst the TARDIS was preparing to materialise atop the Empire State Building. (TV: The Chase)