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Mill Rock Park

Mill Rock Island

This text is part of Parks’ Historical Signs Project and can be found posted within the park.

Mill Rock Island, originally two smaller islands, lies about 1,000 feet off the eastern edge of 96th Street, in the East River. In 1664, William Hallet bought the two islands, later named Great Mill Rock and Little Mill Rock, as well as a nearby point of land on the other side of the river (known as Hallet’s Point in present-day Astoria, Queens) from local Indians. He apparently never occupied the islands, and sometime between 1701 and 1707, John Marsh is believed to have built a tidal mill on one of them, which may explain how Mill Rock got its name.

At the start of the War of 1812, the War Department built a blockhouse with two cannons on Great Mill Rock. Along with fortifications at Hallet’s Point and at Horn’s Hook (site of Gracie Mansion), this chain of blockhouses was hoped to bolster the defenses of New York Harbor and guard the passage into Long Island Sound from the British Navy. In 1821, the blockhouse was destroyed by fire, and for the next 40 or so years squatters took over the island. One squatter, John Clark, is said to have conducted a lively business selling food and drink to the crews and passengers of passing ships.

Toward the end of the 19th century, the U.S. Army Corps of Engineers set up facilities on Great and Little Mill Rock to experiment with explosives for the planned clearing of large obstructions in the East River. On October 10, 1885, the largest planned explosion prior to the atomic bomb annihilated Flood Rock, a nine acre obstacle that had long frustrated East River ship traffic. 300,000 pounds of explosives –prepared at the Army’s island facilities- were detonated, and shocks from the concussion were felt as far away as Princeton, New Jersey. In 1890, rock fill from the blast was used to close the gap between the two islands. Until 1949, the U.S. Army Corps of Engineers continued to use the now unified island of Mill Rock as a work and storage base for the surveying and removing of hazards in the East River and New York Harbor. With the closing of operations that year, the Superintendent of the base, John Smith, became the last person known to have lived on Mill Rock.

In 1953, the federal government sold the island to the Parks Department for $25,000. Commissioner Robert Moses was concerned that if it were sold at public auction, the island might be acquired by commercial interests and huge billboards would be erected there. He arranged for the demolition of the existing buildings and dilapidated docks, and a new dock was constructed. Large amounts of rock were placed along the shore to prevent erosion. Topsoil was brought in, and trees and shrubs were planted.

Mill Rock Island has been used for educational and arts events. In 1969, Commissioner August Heckscher issued a permit for an Avant Garde Festival on the island, which included a hot air balloon ascension, special light displays, and giant sculptures. At the conclusion of the festival, Mill Rock Island was allowed to return to its natural state. In 1978, Parks placed the island under the care of The Neighborhood Committee for Asphalt Green, and granted the Committee consent to use the island as an educational resource. Today, Mill Rock Island serves as a scenic resource. Visible from bustling Manhattan, this natural space stands as a historic landmark and a source of tranquility.

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Mill Rock Park Weather

  • Thu
    Chance Showers
    55°F
  • Fri
    Mostly Cloudy
    66°F
  • Sat
    Mostly Sunny
    67°F
  • Sun
    Breezy
    63°F

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