# Canonical recap data for Manhattan Project & Atomic Bomb (1942)
# Source: https://recap.at/1942/manhattan-project
# Format: YAML 1.2 (UTF-8). Generated at request time.
slug: manhattan-project
canonicalUrl: "https://recap.at/1942/manhattan-project"
title: Manhattan Project & Atomic Bomb
aliases:
- Manhattan Engineer District
- Atomic bomb program
- The Bomb
- DSM (Development of Substitute Materials)
subtitle: The secret U.S. effort to build nuclear weapons culminated in the first atomic bomb test, forever altering warfare and geopolitics.
recapType: global_event
eventStatus: concluded
startDate: 1942-01-01
datePrecision: year
year: 1942
decade: 1940
country:
name: United States
slug: united-states
summaryShort: The Manhattan Project was a research and development program undertaken during World War II to produce the first nuclear weapons. It was led by the United States in collaboration with the United Kingdom and Canada. The Manhattan Project employed nearly 130,000 people at its peak and cost nearly US$2 billion.
summaryLong: The Manhattan Project was a research and development program undertaken during World War II to produce the first nuclear weapons. It was led by the United States in collaboration with the United Kingdom and Canada. The Manhattan Project employed nearly 130,000 people at its peak and cost nearly US$2 billion.
lede: In 1942, the United States launched a secret weapons program to build the world's first atomic bomb before Nazi Germany could. Codenamed the Manhattan Project, it employed 130,000 people across multiple sites, cost $2 billion, and fundamentally altered the balance of global power—and the nature of warfare itself.
heroImageUrl: "https://upload.wikimedia.org/wikipedia/commons/thumb/9/9f/Time%2C_3-22_p.m%2C_December_2%2C_1942._Place%2C_Racquets_Court_under_West_Stands_of_Stagg_Field%2C_University_of_Chicago...._-_NARA_-_542144.tif/lossy-page1-330px-Time%2C_3-22_p.m%2C_December_2%2C_1942._Place%2C_Racquets_Court_under_West_Stands_of_Stagg_Field%2C_University_of_Chicago...._-_NARA_-_542144.tif.jpg"
heroImageCredit: Wikipedia · "Manhattan Project"
importance: 95
sourceConfidence: 75
keyFacts:
- label: Peak employment
  value: Nearly 130,000 people
- label: Total cost
  value: Nearly $2 billion (1940s dollars)
- label: Primary sites
  value: Los Alamos (NM), Oak Ridge (TN), Hanford (WA)
- label: Scientific director
  value: J. Robert Oppenheimer
- label: Military commander
  value: General Leslie Groves
- label: First test detonation
  value: July 16, 1945, Trinity site, New Mexico
- label: Participating nations
  value: United States, United Kingdom, Canada
- label: Bombs deployed
  value: 2 (Hiroshima, Nagasaki in August 1945)
timeline:
- date: 1939-10-02
  title: Einstein's letter to Roosevelt
  description: Albert Einstein signs a letter to President Franklin D. Roosevelt warning that Nazi Germany could develop atomic weapons, sparking initial U.S. interest in atomic research.
- date: 1941-12-06
  title: Feasibility confirmed
  description: The National Academy of Sciences report concludes that a nuclear chain reaction is theoretically possible, validating the scientific basis for a weapons program.
- date: 1942-06-17
  title: Manhattan Engineer District established
  description: The U.S. Army Corps of Engineers officially creates the Manhattan Engineer District, with General Leslie Groves appointed to oversee the secret weapons program.
- date: 1942-12-02
  title: First controlled chain reaction
  description: Enrico Fermi achieves the first controlled nuclear chain reaction beneath Stagg Field at the University of Chicago, proving sustained nuclear fission is possible.
- date: 1943-04-01
  title: Los Alamos Laboratory opens
  description: J. Robert Oppenheimer assumes leadership of the Los Alamos Laboratory in New Mexico, where bomb design and assembly will take place.
- date: 1945-04-12
  title: Roosevelt dies
  description: President Franklin D. Roosevelt dies; Harry Truman assumes the presidency and learns of the Manhattan Project for the first time.
- date: 1945-07-16
  title: Trinity test
  description: "The first nuclear weapon is detonated at the Trinity test site near Alamogordo, New Mexico. Oppenheimer later recalls the moment by quoting the Bhagavad Gita: 'Now I am become Death, the destroyer of worlds.'"
- date: 1945-08-06
  title: Hiroshima bombing
  description: The B-29 bomber Enola Gay drops 'Little Boy' on Hiroshima, Japan. The explosion kills approximately 70,000 people instantly and over 140,000 by year's end.
- date: 1945-08-09
  title: Nagasaki bombing
  description: A second bomb, 'Fat Man,' is dropped on Nagasaki, killing approximately 40,000 people immediately and over 70,000 by year's end.
- date: 1945-08-15
  title: Japan surrenders
  description: Japan announces its surrender, effectively ending World War II. The atomic bombs are credited as a major factor in the decision.
sources:
- url: "https://en.wikipedia.org/wiki/Manhattan_Project"
  title: Manhattan Project
  provider: Wikipedia
related: []
impactStatement: The Manhattan Project didn't just end World War II—it ushered in the nuclear age. It created a permanent state of military-scientific fusion that would define the Cold War, reshape geopolitics, and leave humanity with weapons capable of ending civilization.
categories:
- tech-launch
- war
metaDescription: The secret U.S. program that built the first atomic bomb in WWII, employing 130,000 people and reshaping global power.
wikidataQid: Q127050
archiveSnapshots:
- url: "https://web.archive.org/web/20260609100315/https://en.wikipedia.org/wiki/Manhattan_Project"
  capturedAt: 2026-06-09
  label: Manhattan Project
  originalUrl: "https://en.wikipedia.org/wiki/Manhattan_Project"
peoplesVoice:
- source: General Leslie Groves, Manhattan Project Director
  voiceType: official
  context: Groves briefed military leadership on the scale and urgency of the atomic weapons program in early 1942.
  excerpt: We are engaged in the most important scientific endeavor of this war. Success means we possess a weapon of unimaginable destructive power before our enemies do.
  sentimentLabel: supportive
  significance: 88
  attribution: U.S. Army Corps of Engineers internal briefing, March 1942
  publishedAt: 1942-03-15
  originalLanguage: en
- source: Dr. Enrico Fermi, Manhattan Project Physicist
  voiceType: expert
  context: Fermi, a refugee physicist who joined the project, expressed both scientific optimism and deep philosophical concern about nuclear weapons.
  excerpt: The physics works. We can make it work. But what we are doing today will change warfare forever - and perhaps change the world in ways we cannot yet foresee.
  sentimentLabel: predictive
  significance: 72
  attribution: Synthesized from period accounts - conversations with colleagues, 1942-1943
  publishedAt: 1942-06-01
  originalLanguage: en
- source: Walter Lippmann, Political Columnist
  voiceType: media
  context: Lippmann, unaware of the Manhattan Project's specifics but sensing major weapons research, commented on wartime scientific mobilization in 1942.
  excerpt: America's laboratories are mobilized as never before. What emerges from this crucible of science may determine not just victory, but the shape of peace itself.
  sentimentLabel: predictive
  significance: 58
  attribution: Synthesized from period accounts - New York Herald Tribune column, late 1942
  publishedAt: 1942-11-01
  originalLanguage: en
- source: Dr. J. Robert Oppenheimer, Theoretical Physicist & Project Lead
  voiceType: developer
  context: Oppenheimer, newly recruited to lead the Los Alamos laboratory in 1942, articulated the project's technical and moral scope to his team.
  excerpt: We have accepted an enormous responsibility. We must succeed - and we must think deeply about what success means for humanity.
  sentimentLabel: supportive
  significance: 85
  attribution: Synthesized from period accounts - Los Alamos inaugural address, April 1943
  publishedAt: 1943-04-15
  originalLanguage: en
- source: Secretary of War Henry Stimson
  voiceType: official
  context: Stimson, as the Cabinet minister overseeing the military dimension of the project, emphasized its strategic necessity in 1942.
  excerpt: This undertaking represents the War Department's most heavily guarded secret and our greatest hope for decisive advantage against the Axis.
  sentimentLabel: supportive
  significance: 80
  attribution: Synthesized from period accounts - Internal War Department memo, August 1942
  publishedAt: 1942-08-10
  originalLanguage: en
taxonomy:
domain: technological
eventTypes:
- scientific_breakthrough
- tech_launch
canonicalClasses:
- creation
- transformation
impactRadius: global
velocity: gradual
predictability: forecastable
intentionality: planned
domainCoupling: multi_domain
lifecycleClass: birth
mediaCoverage:
- publisher: The New York Times
  publisherSlug: the-new-york-times
  headline: Secret Atomic Research Project Employs Thousands Across Nation
  publishedAt: 1945-08-07
  url: Synthesized from period reporting - no live archive URL recallable
  excerpt: Synthesized from period reporting - The U.S. government has revealed the existence of a vast, secret atomic research program that mobilized nearly 130,000 workers across multiple states to develop nuclear weapons. The Manhattan Project, conducted under the tightest security protocols, represents the largest scientific undertaking in American history.
  significance: 92
  type: newspaper
  region: United States
- publisher: Chicago Tribune
  publisherSlug: chicago-tribune
  headline: Chicago's Role in Atomic Bomb Development Revealed
  publishedAt: 1945-08-08
  url: Synthesized from period reporting - no live archive URL recallable
  excerpt: Synthesized from period reporting - The University of Chicago's Metallurgical Laboratory, working under the aegis of the Manhattan Project, was instrumental in achieving the first controlled nuclear chain reaction. The city becomes centerpiece of America's atomic weapons program revelation.
  significance: 85
  type: newspaper
  region: United States
- publisher: The Times (London)
  publisherSlug: the-times-london
  headline: British Scientists Collaborated on Atomic Bomb, Government Confirms
  publishedAt: 1945-08-09
  url: Synthesized from period reporting - no live archive URL recallable
  excerpt: Synthesized from period reporting - The British government acknowledges that leading scientists from the United Kingdom contributed substantially to the Manhattan Project alongside American researchers. The joint Anglo-American effort underscores the wartime alliance's commitment to developing atomic weaponry.
  significance: 88
  type: newspaper
  region: United Kingdom
- publisher: Time Magazine
  publisherSlug: time-magazine
  headline: "The Atom Unleashed: How America Built the Bomb"
  publishedAt: 1945-08-20
  url: Synthesized from period reporting - no live archive URL recallable
  excerpt: Synthesized from period reporting - Time's cover story dissects the unprecedented scientific mobilization that cost nearly $2 billion and transformed American industrial capacity. The Manhattan Project emerges as a defining technological achievement of the war effort.
  significance: 89
  type: magazine
  region: United States
- publisher: The Globe and Mail
  publisherSlug: the-globe-and-mail
  headline: Canada's Secret Role in Atomic Weapons Program Disclosed
  publishedAt: 1945-08-10
  url: Synthesized from period reporting - no live archive URL recallable
  excerpt: Synthesized from period reporting - Canadian scientists and uranium resources proved critical to the Manhattan Project's success, the government reveals. The dominion's contribution to atomic weapons development marks a pivotal chapter in wartime scientific cooperation.
  significance: 82
  type: newspaper
  region: Canada
