The Manhattan Project National Historical Park tells the story of the people, the events, and the science and engineering that led to the creation of the atomic bombs that helped bring an end to World War II.
Structures and landscapes from that era allow visitors to explore how the creation of these weapons changed the world and the United States’ role in the world community, and address the subsequent controversy and contribution of the Project to the annals of history and the world in which we live.
The Manhattan Project at Oak Ridge, Tennessee
Several massive Manhattan Project facilities at Oak Ridge enriched uranium for use in Little Boy, the atomic bomb dropped on Hiroshima, Japan on August 6, 1945. Today the story of the Manhattan Project at Oak Ridge includes historic sites, community centers and museums, and highly-secured nuclear research facilities operated by the US Department of Energy.
Nuclear reactors at Hanford (now the Hanford Site) produced plutonium for the Manhattan Project to fuel the first atomic test and the Fat Man atomic bomb dropped on Nagasaki, Japan on August 9, 1945. The story of the Manhattan Project at Hanford encompasses historic facilities and educational centers with the National Park Service, the US Department of Energy and the communities where Hanford workers and their families lived, which are all part of the Tri-Cities region today.
The Manhattan Project Sites at Los Alamos, New Mexico
During World War II, the name “Los Alamos” was classified information. People referred to Los Alamos Laboratory as Project Y, Site Y, or the Zia Project, though locals called it “the hill”—a name that you’ll hear residents use today. The canyons, mesas, and mountains surrounding Los Alamos were an ideal place for workers to escape the pressure of their jobs and relax. Civilian workers and scientists brought their families to “the hill,” and created a sense of community on the isolated mesa-top, even during this immense undertaking. In January of 1943, this secret city had just 1,500 residents. By the time the war ended in 1945, the population of Los Alamos had boomed to an estimated 8,200.
Sites on Laboratory Land
In Los Alamos, New Mexico, Manhattan Project administrators found an ideal location for the secret laboratory where they designed and built the world’s first atomic weapons. These sites, currently not accessible to the public, represent the world-changing history of the Manhattan Project at Los Alamos. Their preservation and interpretation will show visitors the scientific, social, political, and cultural stories of the men and women who ushered in the atomic age. Though the park was established in December 2015, full implementation will take time. At Los Alamos National Laboratory, the Department of Energy is developing phased access to its properties in step with performing its ongoing mission.
TA-18-2 was constructed in 1944 to support implosion diagnostic tests related to Fat Man design development. Experiments using the magnetic method, carried out at Pajarito Site, detected changes in a magnetic field during a high-explosives shot.
TA-18-2 is a robust, cast-in-place concrete bunker. It is known as a battleship building because the west end of the building is bow shaped and shielded with steel plate.
Two Mile Mesa Site, also known as TA-6, was used as an outdoor research area to develop plutonium recovery methods in the event that the Trinity test failed. One of the most visible legacies of this research is a large, 200-ft-diameter concrete bowl built in 1944. The bowl was used for the water recovery method, which involved detonating high explosives experiments using natural uranium as a stand- in for plutonium.
The test assemblies were placed in the center of the bowl in a redwood water tank on top of a wooden tower structure. Each shot used up to 10 pounds of explosives and up to 500 gallons of water. Shake tests of explosives and other test shots supporting wartime weapons research were also conducted at the structure.
During Project Y, Los Alamos researchers also developed the Gun Site, known in 1943 as Anchor Ranch Proving Ground, to design and test nuclear weapon prototypes. At this site, scientists, engineers, and ordinance experts conducted experiments on the inner workings of a “gun-type” atomic bomb design, hence the site’s name.
Built to protect researchers during the numerous “gun-assembly” tests, this site’s concrete and earthen bunkers were constructed in a natural drainage, which placed the tests above the bunkers and lessened the hazards of these experiments for the staff performing them.
The bunkers at Gun Site underwent extensive concrete repairs in 2012, including reconstruction of the concrete parapet wall and the addition of a concrete cap to drain water from the top. However, the concrete cap failed and allowed further degradation. To address this, and prevent further damage to the structures, workers removed the crumbling concrete from the 2012 project.
More than 12 testing areas were developed at Los Alamos in late 1944 and early 1945 to support the design of a new plutonium weapon. This research included the use of varied diagnostic methods to understand the inner workings of implosion, an inward explosive force that was key to the Fat Man weapon design.
Built in late 1944, TA-11 supported experiments that relied on the betatron diagnostic method. The method involved the detonation of a test implosion between two buildings, one housing a betatron machine, which emitted X-rays at the instant of the explosion, and the other housing a cloud chamber to record the test data.
TA-12-4, built in 1944, is a firing pit constructed of heavy timber for use in high-explosives experiments that supported implosion research. The Los Alamos Terminal Observation Group used TA-12 as its firing site. Physical remains of explosives firing tests were examined after each shot, hence the term “terminal observation.” World War II facilities included the firing pit, a personnel shelter, and several storage buildings and magazines. The pit structure is 12-ft deep and capped with an 8-ft-square steel lid. The sides of the pit are lined with 3/4-in. steel plate, which was designed to protect the structure from explosive blasts.
Originally built in 1914 by Ashley Pond as an office for a private Sportman’s Club, the cabin was used by physicist Emilio Segrè’s group during the Manhattan Project to support plutonium chemistry research.
TA-14-6 is a small, wood-frame building that was constructed in 1944 as a darkroom and shop to support small scale implosion tests. At Q-Site (TA-14), cylinder implosions were studied using the flash photography method. This implosion diagnostic tool relied on high-speed photographic equipment, including the rotating prism camera. In addition to the flash photography implosion experiments, terminal observation experiments were also conducted at Q-Site. Wartime facilities included a control building, high-explosives magazines, firing chambers, and the TA-14-6 shop and darkroom building.
The Quonset Hut
Building TA-22-1, a Quonset™ hut, is one of the most historically significant properties at the Laboratory. Manhattan Project scientists and engineers worked on the final design of the Fat Man weapon in this facility, perfecting the “trap door” design shortly before the end of the war. Fat Man’s high-explosives sphere and associated components were assembled in this building and then transported to Tinian Island. After the war, the building was used as a detonator research facility for almost 40 years.
TA-16-58, constructed in 1944, is a one-story, single-room, high-explosives storage magazine. This small building was constructed with a reinforced-concrete floor and walls. The magazine is encircled by a protective earthen berm, and its roof is built of wood to serve as an upwards path for the force of an accidental explosion. This building is the last remaining high-explosives facility built specifically to support S-Site operations during the Manhattan Project.
The high-bay addition at TA-18-1 was constructed in1946, at the end of the Manhattan Project era, and supported criticality research at the wartime Laboratory’s Pajarito Site. This building addition was the location of the May 21, 1946, criticality accident, which occurred during an experiment known as “dragon-type experiment” and led to the death of scientist Louis Slotin.
TA-18-1 is known as the Slotin Building today. It is a relatively small, wood-frame building with asbestos-type shingles, and was built according to typical World War II temporary construction standards. After the war, the building supported Cold War research and was later used as a shop.
V-Site was constructed to support the assembly of the Fat Man implosion weapon. It was also used to assemble the high-explosives sphere for the Trinity device or Gadget. The site originally consisted of six buildings, but four were destroyed during the May 2000 Cerro Grande Fire. The first building at V-Site was built in early 1944. TA-16-517, as it is known today, is a small triangular-shaped building surrounded by an earthen berm.
Building 517 supported early tests of the first Fat Man prototypes to ensure that key components could withstand cold temperatures and vibration. Additional shop buildings, a high-bay assembly building, and a covered storage area were constructed at V-Site in late 1944 to support the assembly of the Trinity device. During the week of July 9, 1945, the high-explosives package for the Gadget was assembled at V-Site in TA-16-516, the high-bay building.
In downtown Los Alamos, the Manhattan Project National Historical Park experience is a partnership between the Department of Energy, the National Park Service, Los Alamos County, the Los Alamos Historical Society, and private landowners.
Ashley Pond is named after the founder of the Los Alamos Ranch School. Today it is a public park and center for community events.
The homes on this street were built for the Los Alamos Ranch School and were adapted during the Manhattan Project for use by scientists. The street got its name because they were only homes in town with bathtubs during WWII.
Bradbury Science Museum
Over 60 interactive exhibits trace the history of the Manhattan Project, and describe Los Alamos National
Laboratory's defense and technology research projects.
Fuller Lodge was built in 1928 as the dining hall for the Los Alamos Ranch School. During Project Y, the Lodge hosted community activities for lab employees. On Wednesdays come explore this wonderful log building!
Hans Bethe House
Chemist Edwin McMillan and physicist Hans Bethe, both Nobel Prize winners, lived in this house. Inside, you will find the Harold Agnew Cold War galleries, part of the Los Alamos History Museum. Tickets are available at the History Museum.
Ice House Memorial
This memorial contains original stone from the Ranch School’s ice house, which was torn down in 1957. Project Y scientists used the ice house to assemble the nuclear components of the Trinity gadget, the first tested atomic device.
Los Alamos History Museum
Built as the infirmary for the Ranch School in 1918, it later served as a guest cottage for Ranch School visitors and was Gen. Leslie Groves’ favorite place to stay in Los Alamos. This museum features exhibits
on the Manhattan Project, as well as the people of Los Alamos from ancient through contemporary times.
Oppenheimer & Groves Sculpture
You can see sculptures of Dr. J. Robert Oppenheimer, scientific head of the Manhattan Project, and Gen. Leslie Groves, military head of the Project.
Stone Power House
This structure was built in 1933 to house the Ranch School’s electrical generator. A er remodeling it in 1944–1945, explosives expert George Kistiakowsky lived here.
Manhattan Project Visitor Center
Pick up your park guide, get one of the special three-part stamps in your passport, see a short film about the Project, and pick up your Junior Ranger booklet for the kids. Welcome to your tour of Project Y, the Manhattan Project’s Los Alamos Site!
This building was the favorite mess hall for the military members of the Project. Now it is the Los Alamos
Performing Arts Center.
Women's Army Corps Dormitory
This dormitory housed some of the WAC staff stationed here. Now it is the privately-owned Christian Science Reading Room; no visitors, please.
Virtual tour of the historical sites
Discover the stories, people, and locations behind the Manhattan Project with our interactive virtual tour.