Manhattan Project

American  

noun

1. U.S. History. the unofficial designation for the U.S. War Department's secret program, organized in 1942, to explore the isolation of radioactive isotopes and the production of an atomic bomb: initial research was conducted at Columbia University in Manhattan.

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Manhattan Project British  

noun

1. (during World War II) the code name for the secret US project set up in 1942 to develop an atomic bomb

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Manhattan Project Cultural  

1. The code name for the effort to develop atomic bombs (see also atomic bomb) for the United States during World War II. The first controlled nuclear reaction took place in Chicago in 1942, and by 1945, bombs had been manufactured that used this chain reaction to produce great explosive force. The project was carried out in enormous secrecy. After a test explosion in July 1945, the United States dropped atomic bombs on the Japanese cities of Hiroshima (see also Hiroshima) and Nagasaki.

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Etymology

Origin of Manhattan Project

Extracted from U.S. Army Corps of Engineers Manhattan District and DSM (Development of Substitute Materials) Project

Example Sentences

Historically, Los Alamos served as the top-secret heart of the Manhattan Project, where the first atomic bombs were designed and built on an expedited timeline.

From Barron's • Apr. 23, 2026

Many members believe they’ve lost loved ones to radiation, or were themselves likely impacted by early-life exposure as children of Manhattan Project engineers.

From Los Angeles Times • Mar. 27, 2026

Historically, when technology is decisive in the defense space—think the Manhattan Project or aerospace in the early days of the Cold War—the government and industry align quickly and tightly.

From Barron's • Mar. 5, 2026

Given the scale of Beijing’s financial and policy support and the secretive nature of some of these programs, it’s safe to say mastering fusion has become China’s Manhattan Project.

From The Wall Street Journal • Feb. 23, 2026

By the end of the war, Groves calculated, its construction, engineering, and electricity would cost more than a half billion dollars, making it the single most expensive component of the Manhattan Project.

From "Big Science" by Michael Hiltzik