In 1834, the states agreed that islands in the area would belong to NY, while NJ would get rights to half of the waterway. Ellis Island was expanded by dumping ballast from ships and debris from subway tunnel excavation, and it was decided that this artificial part of the island took up part of NJ's waterway access. The expanded portion of Ellis Island (about 90%) became part of NJ, with the original, natural footprint of the island became NY property that is completely surrounded by a New Jersey border.