Mill Rock Park

Mill Rock Park occupies an 8.64-acre island in the East River opposite East 96th Street, situated in the treacherous waters of Hell Gate where the East River, Harlem River, and Long Island Sound converge. The island is one of the least-known and least-accessible parks in the entire NYC Parks system.

The island's name derives from a tide mill that operated on the rocky outcropping in colonial times, harnessing the powerful tidal currents of Hell Gate to grind grain. The waters around the island were once among the most dangerous navigable channels on the Eastern Seaboard, with submerged rocks and whirlpools that caused hundreds of shipwrecks.

The Army Corps of Engineers cleared the Hell Gate channel in two massive blasts. The first, in 1876, destroyed Hallets Point Reef and was felt as far away as Princeton, New Jersey. The second and far larger came in 1885, when engineers annihilated Flood Rock, a submerged reef adjacent to Mill Rock that was the primary obstacle to navigation, with roughly 300,000 pounds of explosives in what was then among the largest planned detonations in history. Rubble from Flood Rock was later used to fill the gap between Great Mill Rock and Little Mill Rock, joining them into the single island that exists today.

Today Mill Rock is an uninhabited nature preserve, home to nesting waterbirds including great egrets, night herons, and cormorants. The island's isolation from human activity has allowed it to become a valuable wildlife habitat in the otherwise heavily developed East River corridor.

Mill Rock Park is technically part of the NYC Parks system but has no regular public access, no facilities, and no programming. It represents a fascinating category of urban parkland: a wild island in the middle of a great city, visible from the surrounding shores but separated from the human world by the swift, dangerous currents of Hell Gate.