Colonial and Early American Development

Between 1701 and 1707, John Marsh built a tidal mill on Great Mill Rock, which gave the islands their name. The rocks and islands were notable for their dangerous currents and were seldom inhabited. During the War of 1812, the U.S. War Department constructed a blockhouse and installed two cannons as part of a defensive line—Mill Rock Fort was established in 1812 as a coastal battery to guard New York Harbor against possible British attack. The blockhouse burned down in 1821, after which the islands sporadically hosted squatters and subsistence farmers, including John Clark, who operated a small trading post and Sandy Gibson, who ran a farm from 1840 to 1898.

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Conversion to Parkland and Public Ownership

In 1953, the federal government sold Mill Rock Island to the New York City Department of Parks for $25,000, thanks to Parks Commissioner Robert Moses. He prevented private commercial development and billboard installations, arranged for demolition of derelict buildings, constructed a new dock, stabilized the shoreline with rocks, added topsoil, and planted trees and shrubs. Mill Rock Island began serving as a scenic, natural, and educational space. In 1969, the Avant Garde Festival took place there, featuring performances, a hot air balloon ascension, giant sculptures, and light shows. It was returned to a natural state soon after, and since 1978, it’s been managed by the Neighborhood Committee for Asphalt Green, which has used it for educational programs.

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Current Status: Sanctuary and Historic Landmark

Today, Mill Rock Island is uninhabited, closed to the public, and serves as a bird sanctuary and ecological resource. The grounds are used for wildlife and environmental observation, and the island remains visible off East 96th Street as a green patch among the urban river. Its blend of military, engineering, farm, and arts history gives it continued local significance as a tranquil landmark.

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Hell Gate and Army Engineering Projects

The late 19th century saw significant engineering activity at Mill Rock due to the hazards of Hell Gate—a treacherous stretch of the East River dangerous for ships. The U.S. Army Corps of Engineers undertook massive rock removal projects, including setting up experimental testing bases on Mill Rock. On 10 October 1885, over 300,000 pounds of explosives were used to destroy the adjoining Flood Rock, an infamous obstruction; the shockwave was felt as far as Princeton, New Jersey. The rubble from this huge blast filled the gap between Great and Little Mill Rock, uniting them as Mill Rock Island by 1890.

Indigenous Context and Early Colonial Ownership

Mill Rock Island’s history begins with the Lenape people, who lived along the shores and islands of the East River for thousands of years before European settlement. In 1664, local settler William Hallet purchased two separate rocky outcrops (Great Mill Rock and Little Mill Rock) from Native Americans, as well as adjacent land on the Manhattan and Queens sides of the river.

Military, Utility, and Storage Usage

Until 1949, Mill Rock Island served as a work and storage base for the Army Corps of Engineers, supporting survey and hazard removal operations. The last known resident, Superintendent John Smith, left when military facilities closed and the island was decommissioned. By mid-century, the island was largely vacant except for abandoned docks and buildings.

Notable Events and Incidents

Mill Rock Island’s history includes eccentric residents, large-scale engineering projects, and avant-garde arts events. The transformative 1885 explosion to remove Hell Gate obstacles was at the time the largest planned detonation before atomic bomb testing. Subsequent stories of squatters, subsistence living, and its cameo as a unique artistic site all contributed to its varied character across centuries.

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Squatter Settlement and Farm Era

From the mid-1800s, Mill Rock was occupied by various squatters, including Sandy Gibson, who moved his household and livestock to the island. John Clark sold food and supplies to passing ships, and Gibson’s tenure saw the island used for subsistence farming, fishing, and trading. Charles Leland acquired the island briefly in the late 1800s, after which Gibson stayed on as a tenant, catching eels and flounder for food. The island became a colorful local character spot, with stories of its eccentric residents and makeshift farm structures.

Mill Rock

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Uncover the unique character and hidden corners of the harbor.

Community Organizations

Articles and Books

Gotham Unbound by Ted Steinberg

"New York's Lost Islands: Mill Rock" - Untapped New York Documentary

"Before Central Park: Native Americans" - Central Park Conservancy Blog

"Mill Rock Fort - FortWiki Historic U.S. and Canadian Forts," 2019

"Mill Rock | A Great Big City" - Urbanist blog series

"Mill Rock | This island in the East River started out as two..." - Flickr Photo Essay

"Mill Rock Island - NYC You Don't See" - Blogger Mr. Beller, 2010

"Mill Rock | The New Yorker," 1938 - The New Yorker Magazine

"Mill Rock Island - NYC Parks" - New York City Department of Parks and Recreation