It contains several islands including Governors Island, near the mouth of the East River, as well Ellis Island, Liberty Island, and Robbins Reef which are supported by a large underwater reef on the New Jersey side of the harbor. The reef was historically one of the largest oyster beds in the world and provided a staple for the diet of all classes of citizens both locally and regionally until the end of the 19th century, when the beds succumbed to pollution.[5]