PLUM ISLANDPlum Island: A History

The history of Plum Island is rich and varied, with changing times, historical context, and national challenges changing the use of the island and its purpose.

Here are highlights of the Island’s history:

Colonial Background, 1640s–1700s: Plum Island is incorporated into English colonial land grants on Long Island’s North Shore. The island is Used mainly for grazing livestock, fishing access, and maritime navigation reference

American Revolution, 1775–1783: No major battle occurs on the island, but it sits inside a strategic maritime corridor between Long Island, Connecticut, and New England ports

British Naval Control, 1776–1783: After occupying New York City, British forces dominate Long Island Sound. Plum Island was likely used for naval observation, anchorage, and patrol support.

It also served as part of Britain’s blockade network against colonial shipping.

1783–1812: The island is returned to private use, and is mostly used for agricultural and maritime business. There is no permanent federal presence on the island.

War of 1812: The British fleets again control Long Island Sound, and the vulnerability of eastern Long Island becomes clear. This leads directly to later coastal fortification planning.

1815–1880s: The island is privately owned and used for fishing stations, small farms, and navigation markers. No major infrastructure is built on the island.

Strategic Reassessment (late 1800s): The rise of steel warships and long-range artillery increase U.S. fears naval attacks on New York and New England.

Spanish–American War as a Catalyst (1898): TheWar exposes weakness of U.S. coastal defenses. Congress authorizes major harbor fortifications.

Establishment of Fort Terry. In 1899 the U.S. Army acquires Plum Island, and Fort Terry is constructed as part of the “Endicott System.” The purpose of the fort was to protect Long Island Sound, the approaches to New London, and the eastern routes to New York Harbor.

Infrastructure (1899–1915): The firs fifteen years of the 20th Century saw the building on the island of concrete gun batteries, ammunition depots, barracks, searchlight stations, and submarine mine controls.

Early 20th Century Military Role, 1900–1918: The island is manned by the United States Army, which places large-caliber artillery on the island to help guard shipping lanes.

Interwar Decline, 1920s–1930s: Following the First World War, the fortifications on the island became obsolete as new aircraft and submarines reduce usefulness of shore facilities. The Army’s garrison on the island is reduced.

World War II Reactivation, 1939–1945: Fort Terry reactivated, and anti-submarine defenses, radar and coastal surveillance, and training facilities are built.