From 1890 to 1934, the federal government expanded Ellis Island through land reclamation to accommodate its immigration station.

An unusual clause in New Jersey's colonial land grant named the territory as being "westward of Long Island, and Manhitas Island and bounded on the east part by the main sea, and part by Hudson's river,"[2] rather than at the river's midpoint, as was common in other colonial charters.

[10] Jurisdictional disputes re-emerged in the 1980s, with the renovation of Ellis Island,[11] and then again in the 1990s, with proposed redevelopment of the south side.

[12] In 1992, the Court of Appeals for the Second Circuit ruled that New York's law should apply in a case that happened on the new part of the island.

[12] The Supreme Court appointed Paul R. Verkuil to be special master to gather evidence in the decision.

[9][14][15] Both states jointly negotiated a post-trial settlement to decide the borders in accordance with the Supreme Court's decision.