The Trinity Test

On July 16, 1945, the first test detonation of an atomic bomb took place at the Trinity Site, Alamogordo, New Mexico as part of the Manhattan Project. From the article:

"The Trinity Test

At the time World War II broke out in Europe, America’s scientific community was fighting to catch up to German advances in the development of atomic power. In the early 1940s, the U.S. government authorized a top-secret program of nuclear testing and development, codenamed “The Manhattan Project.” Its goal was the development of the world’s first atomic bomb. Much of the research and development for the project occurred at a facility built in Los Alamos, New Mexico. In July 1945, Los Alamos scientists successfully exploded the first atomic bomb at the Trinity test site, located in nearby Alamogordo.

The Manhattan Project
Beginning in 1939, some American scientists–many of them refugees of fascist regimes in Europe–advocated the development of ways to use nuclear fission for military purposes. By late 1941, the federal government’s Office of Scientific Research and Development, headed by scientist Vannavar Bush, took control of the project. After the United States entered World War II, the U.S. Army Corps of Engineers was tasked with building the great quantity of necessary plants, laboratories and other research and testing facilities.

Much of the initial research had been performed at Columbia University in New York City, and the top-secret research was thereafter known by the code name Manhattan Project. More than 30 laboratories and sites and more than 130,000 people were eventually involved in different facets of nuclear research and development, with three primary locations–in Oak Ridge, Tennessee; Richland, Washington; and Los Alamos, New Mexico–that became virtual top-secret atomic cities.

How Production Worked
A medium-sized reactor built at Oak Ridge produced uranium-235 and plutonium, both of which would be used as vital components in the atomic bomb. The Oak Ridge facility produced the majority of uranium used to build the “Little Boy” bomb that would be dropped over the Japanese city of Hiroshima in August 1945.

Within a year, the world’s first large-scale plutonium reactor was in service at Hanford, and by early 1945 shipments of enriched plutonium from the plant’s three reactors were being sent to Los Alamos every five days. This material would be used in the first atomic bomb testing, as well as in “Fat Man,” the atomic bomb dropped over Nagasaki. Finally, The facility at Los Alamos served as the primary “think tank” of the Manhattan Project. Its engineers, led by J. Robert Oppenheimer, were responsible for the final construction, testing and delivery of the bombs.

The Trinity Test
At 5:30 a.m. on July 16, 1945, Los Alamos scientists detonated a plutonium bomb at a test site located on the U.S. Air Force base at Alamogordo, New Mexico, some 120 miles south of Albuquerque. Oppenheimer chose the name “Trinity” for the test site, inspired by the poetry of John Donne. The test had been scheduled for 4 a.m., but when the time came it was raining, and the appointed hour was pushed back to 5:30. Tensions ran high at the test site, where those assembled included the scientist Enrico Fermi–who had directed the first nuclear chain reaction in December 1942–U.S. Army Brigadier General Leslie Groves, Bush, Oppenheimer and others.

When the bomb was finally detonated atop a steel tower, an intense light flash and sudden wave of heat was followed by a great burst of sound echoing in the valley. A ball of fire tore up into the sky and then was surrounded by a giant mushroom cloud stretching some 40,000 feet across. With a power equivalent to around 21,000 tons of TNT, the bomb completely obliterated the steel tower on which it rested. The nuclear age had begun."