On December 28, 1942, President Franklin D. Roosevelt authorized the "Manhattan Project"
with the goal of weaponizing nuclear energy. Under the direction of nuclear physicist
J. Robert Oppenheimer and Lieutenant General Leslie R. Groves, thousands of people
worked under strict secrecy at sites throughout the United States.
On July 16, 1945, years of research and design culminated in the detonation of the
worlds first atomic bomb northwest of Alamogordo, NM. Two months later, Groves
and Oppenheimer returned to the site (above) for photographs.
Photo courtesy of the Library of Congress.
On July 16, 1945, scientists led by civilian physicist J. Robert Oppenheimer and Lieutenant General Leslie R. Groves successfully tested a weaponized release of atomic energy in the New Mexican desert. The blast—known as the "Trinity Test"—was the culmination of years of research conducted at sites throughout the United States as part of the Manhattan Project. The test produced a 22 kiloton blast and changed the course of World War II and the future of international relations.
Atomic research was underway at a number of universities in the United States in the late 1930s, including studies led by Ernest Lawrence at the University of California at Berkeley's Radiation Laboratory. Enrico Fermi and Leo Szilard also led studies at Columbia University and later the University of Chicago. Encouraged by these teams' research, President Franklin D. Roosevelt approved establishment of the Manhattan Engineer District—"The Manhattan Project"—on August 13, 1942, naming Lieutenant General Leslie R. Groves to oversee research into weaponizing atomic energy.
In October 1942, Groves selected University of California at Berkeley physicist J. Robert Oppenheimer to lead weapons research, and Oppenheimer chose a site near Los Alamos, NM, to conduct his work. On December 2, 1942, Enrico Fermi's University of Chicago team successfully initiated the world's first, self-sustaining chain reaction. Encouraged by this major development in atomic research, President Franklin D. Roosevelt approved funding for The Manhattan Project's research
Groves and Oppenheimer quickly began moving staff to sites throughout the United States including the primary research facility at Los Alamos, NM, and uranium processing installations in Benton County, WA; and Oak Ridge, TN, along with numerous smaller supporting facilities like those in Ames, IA; Morgantown, WV; and Sylacauga, AL. By early 1944, the scientists had successfully developed the infrastructure necessary to sustain the nation's atomic weapons program and produced designs for uranium- and plutonium-fueled bombs by mid-1945.
On July 13, 1945, the Manhattan Project scientists began assembling the plutonium bomb—nicknamed "The Gadget"—in a remote area of New Mexico's Socorro County, chosen as the site for the "Trinity Test." Upon completion, it was hoisted to the top of a 100-foot steel tower and armed late in the evening of July 15. As American B-29s circled overhead and scientists and military personnel observed from the ground, the device exploded at 5:29 a.m., releasing energy equivalent to 22 kilotons of TNT. The heat from the blast melted the nearby sand into glass and according to an eyewitness account, "the whole country was lighted by a searing light with the intensity many times that of the midday sun." A mushroom cloud of radioactive smoke and debris rose more than 7 miles into the atmosphere and people reported feeling and hearing the blast more than 100 miles away. Years later, Oppenheimer recalled that a line from the Hindu scripture Bhagavad Gita came to mind upon witnessing the atomic blast: "Now I am become Death, the destroyer of worlds."
President Harry S. Truman authorized use of the untested uranium bomb ("Little Boy") and plutonium bomb ("Fat Man") on Japan in late July 1945. On July 25, Acting Army Chief of Staff Thomas Handy ordered Commanding General Carl Spaatz of the Army Air Force's 509th Composite Group to target the Japanese cities of Hiroshima, Kokura, Niigata, and Nagasaki, Japan with atomic weapons. On August 6, 1945, a B-29 bomber named Enola Gay left its base on the Pacific island of Tinian (Commonwealth of Northern Mariana Islands) for Hiroshima, Japan, carrying the 9,700 pound "Little Boy" uranium bomb. The bomb detonated 1,900 feet above the city at 8:15 a.m. local time. On August 9, the plutonium bomb "Fat Man" carried by a B-29 named Bock's Car exploded above Nagasaki, Japan. Japan offered to surrender to the Allies the next day, and General Douglas MacArthur formally accepted Japan's unconditional surrender aboard the USS Missouri on September 2, 1945.
You can learn more about the Manhattan Project and Trinity Test using census data and records. For example:
After years of research, the Manhattan Project successfully detonated the world's first nuclear device at 5:29 a.m., on July 16, 1945. Conducted 75 miles northwest
of Alamogordo, NM, the Trinity Test released between 18 and 22 kilotons of explosive energy proving that atomic energy could be weaponized.
The U.S. Army erected a monument at the detonation site in 1965. On December 21, 1965, The U.S. National Parks Service declared the Trinity Test Site and more
than 50,000 acres surrounding the site—now part of the White Sands Missile Range—a National Historic Landmark district. On October 15, 1966, it was listed
on the National Register of Historic Places.
Image courtesy of the National Parks Service.
In 2017, the American Community Survey estimated that the United States was home to 5,930 nuclear engineers and 3,361 nuclear technicians.
In addition to academic pursuits, many of these professionals work at nuclear electric power generation facilities (NAICS 221113); pharmaceutical manufacturers specializing in radiology and nuclear medicine (NAICS 325412); and naval ship building and repairing (NAICS 336611).
Physicist Albert Einstein (shown above participating in the 1950 Census) and his wife immigrated to the United States in 1933 and settled in Princeton, NJ. He became a permanent resident while working at the Institute for Advanced Study in 1935, and an American citizen in 1940.
Despite being one of the world's premier physicists, Einstein's pacifism and socialist beliefs led President Franklin D. Roosevelt's administration to prohibit Einstein from participating in the Manhattan Project. Instead, Einstein lent his expertise to the U.S. Navy by evaluating weapons systems and raising money for the war effort.
Use census data and records to learn more about Einstein and his research at our March 2019 Web page commemorating the physicist's 140th birthday.