THE MANHAT TAN PROJEC T 

NATIONAL HISTORICAL PARK

National Park Service

U.S. Department of the Interior

MANHATTAN PROJECT NATIONAL HISTORICAL PARK 

The Manhattan Project National Historical Park is one of the nation’s newest 

national parks. Established in November 2015, the park preserves portions of the 

World War II-era sites where the United States developed the world’s first atomic 

weapons. This unique park, managed in partnership by the National Park Service 

and the Department of Energy, will provide visitors the opportunity to walk in the 

footsteps of J. Robert Oppenheimer at Los Alamos, New Mexico; visit Hanford, 

Washington, to stand face to face with the nuclear reactor that produced the material 

for the first atomic test; and learn about the dedication of the Calutron Girls in Oak 

Ridge, Tennessee, who helped the United States win the race against Nazi Germany 

to develop an atomic bomb. The Manhattan Project and its legacy is a complex story. 

It’s the story of more than 600,000 Americans leaving their homes and families to 

work on a project they were told was vital to the war effort. It’s the story of generals, 

physicists, chemists, mathematicians, and engineers pushing and broadening the 

limits of human knowledge and technological achievement in ways never before 

imagined. It is also the story of the death and destruction associated with World 

War II, and a new weapon capable of unimagined levels of devastation. A visit to the 

Manhattan Project National Historical Park provides an opportunity to view the sites 

that helped the United States end World War II and challenges us to think about how 

the world has changed with the dawn of the nuclear age.

THE MANHATTAN PROJECT

The Manhattan Project was an unprecedented, top-secret program implemented 

in the United States during World War II to design and build an atomic bomb. The 

discovery of nuclear fission in Germany suggested the possibility of a nuclear chain 

reaction with the potential release of enormous amounts of energy. Concerned, Leo 

Szilard prompted Albert Einstein in August 1939 to send a letter to President Franklin 

D. Roosevelt, warning that an “extremely powerful bomb” might be constructed. 

Fearing ongoing research and development by Nazi Germany, Roosevelt initiated 

federal funding for uranium research.

By 1942, with the United States at war, officials concluded that an atomic bomb 

could be designed, built, and used in time to influence the outcome of the war. To 

accomplish this task, the US Army Corps of Engineers established the Manhattan 

Engineer District, headed by Brigadier General Leslie Groves. This effort, combining 

military, scientific, and industrial resources and involving hundreds of thousands of 

workers at many sites across the country, was largely kept secret for the duration of 

the project. 

Scientists theorized there were two potential paths to a bomb using uranium-235, 

which comprises about one percent of naturally occurring uranium, or the newly 

discovered element plutonium, which could be created from a controlled chain 

reaction with uranium. Both paths required the use of expensive and unproven 

processes and success was not guaranteed. As a result, the decision was made to 

move forward with both paths. For the uranium bomb, a massive industrial complex 

was built at Oak Ridge, Tennessee, to pursue the three separate technologies to enrich 

uranium at the same time. A pilot reactor and chemical separation plant were also 

constructed at Oak Ridge to test the plutonium production process. For full scale 

plutonium production, a second enormous industrial complex was built at Hanford, 

Washington. Workers built and operated huge reactors, chemical separations plants, 

and fuel fabrication and research facilities. Despite the speed with which the facilities 

were engineered and built, production at both sites was slow and difficult. It was not 

until mid-1945 that sufficient amounts of uranium-235 and plutonium were available 

for construction of the first bombs.

Building the bombs was not an easy task; it required extensive experimentation 

and precise calculations to obtain the optimum specifications. In early 1943, 

General Groves set up a bomb design and development laboratory, with some of 

the world’s foremost scientists under the leadership of J. Robert Oppenheimer, at 

the isolated Los Alamos site in northern New Mexico. The uranium bomb used a 

fairly straightforward gun method for creating a critical mass and nuclear explosion. 

However, in 1944, scientists determined that the gun method would not work for 

plutonium, and they turned to the theoretical and complex implosion method. 

Uncertain it would work, a plutonium device was tested at the Trinity site in southern 

New Mexico on July 16, 1945.

As the project moved closer to the use of the first atomic bomb, ethical questions 

arose in the minds of some who understood the project’s intent; however, scientists 

and politicians were primarily concerned with ending the war as quickly as possible. 

With Germany out of the war, the first uranium bomb was dropped on Hiroshima, 

Japan, on August 6, 1945. When Japan did not surrender, a plutonium bomb was 

dropped on Nagasaki, Japan, on August 9. On August 14, Japan announced its 

surrender and World War II ended.

The Manhattan Project is a highly significant chapter in United States history. It 

ushered in the nuclear age, determined how the next war, the Cold War, would be 

fought, and served as the model for the remarkable achievements of American “big 

science” during the second half of the twentieth century. The Manhattan Project also 

raised ethical and moral questions among scientists and citizens alike—questions that 

continue to this day.

Y-12 Oak Ridge, TN Enrico Fermi J. Robert Oppenheimer and Gun Site, Los Alamos, NM

Brigadier General Leslie Groves

Journalist William L. Laurence, New York Times, September 26, 1945

3⁄4 inch Bronze Commemorative Pin 

made by Whitehead & Hoag Co. and 

issued for service on the project.

“The Atomic Age began at exactly 5:30 Mountain War Time on the morning of July 16, 1945, on a stretch of semidesert land about 50 airline miles from Alamogordo, New Mexico. And just at that instance there rose from the 

bowels of the earth a light not of this world, the light of many suns in one.” 
Los Alamos, New Mexico 

Located on a remote mesa in New Mexico, more than 6,000 scientists and support 

personnel worked to design and build the atomic bombs. The park currently 

includes three areas at Los Alamos. Gun Site, which includes three bunkered 

buildings (TA-8-1, TA-8-2, and TA-8-3), and a portable guard shack (TA-8-172). 

These buildings were associated with the design of the “Little Boy” bomb. V-Site 

includes buildings TA-16-516 and TA-16-517, which were used by laboratory 

personnel to assemble components of the Trinity device in July 1945. Pajarito 

Site includes the Slotin Building (TA-18-1), the Battleship Bunker (TA-18-2), and 

the Pond Cabin (TA-18-29). Pajarito Site was used during the war for plutonium 

chemistry research and later became the main site for critical assembly work at Los 

Alamos after the war.

Oak Ridge, Tennessee 

The Clinton Engineer Works, which became the Oak Ridge Reservation, was 

the administrative and military headquarters for the Manhattan Project and 

home to more than 75,000 people who built and operated the city and industrial 

complex in the hills of East Tennessee. The Oak Ridge Reservation included three 

parallel industrial processes for uranium enrichment and experimental plutonium 

production. At Oak Ridge, the park includes the X-10 Graphite Reactor National 

Historic Landmark, a pilot nuclear reactor which produced small quantities 

of plutonium; Buildings 9731 and 9204-3 at the Y-12 complex, home to the 

electromagnetic separation process for uranium enrichment; and the site of the K-25 

Building, where gaseous diffusion uranium enrichment technology was pioneered. 

Buildings 9731, 9204-3 and K-25 together enriched a portion of the material for the 

uranium bomb.

Hanford, Washington 

The Hanford Engineer Works was built to create large quantities of plutonium at a 

roughly 600-square-mile site along the Columbia River in Washington State. More than 

51,000 workers at Hanford constructed and operated a massive industrial complex 

to fabricate, test, and irradiate uranium fuel and chemically separate out plutonium. 

The Hanford landscape is also representative of one of the first acts of the Manhattan 

Project, the condemnation of private property and eviction of homeowners and 

American Indian tribes to clear the way for the top-secret work. At Hanford the park 

includes: the B Reactor National Historic Landmark, which produced the material for 

the Trinity test and plutonium bomb; the Hanford High School in the Town of Hanford 

and Hanford Construction Camp Historic District; Bruggemann’s Agricultural 

Warehouse Complex, White Bluffs Bank, and Hanford Irrigation District Pump House, 

which together provide a glimpse into the history of the Hanford area before the arrival 

of the Manhattan Project. The T Plant, a chemical separations canyon, will not be in the 

Park initially, but visitors will learn about its vital role at other locations in the park.

Pond Cabin, Los Alamos, NM X-10 Graphite Reactor, Oak Ridge, TN B Reactor, Hanford, WA

A PARTNERSHIP EFFORT

Manhattan Project National Historical Park is a partnership park. The National 

Park Service is responsible for administration, interpretation, and education at the 

three sites and will provide technical assistance to resource preservation efforts. 

The Department of Energy will continue to have responsibility for management, 

operations, maintenance, and historic preservation of the historic Manhattan 

Project sites now under their jurisdiction. Other agencies, communities, 

organizations, and associated tribes may also become involved to tell the full story 

of the Manhattan Project.

VISITING THE PARK

A visit to the Manhattan Project National Historical Park will be different from 

a visit to many other national parks. Many of the properties included in the 

park are located in areas that are being cleaned up or are still active nuclear 

facilities. Because of safety and security concerns some facilities may not 

be immediately accessible and others may only accessible on organized bus 

tours. The National Park Service and the Department of Energy are working 

together to safely expand access to the facilities included in the park. We are 

also working with partners in local communities and from around the world 

to tell the complete story of the Manhattan Project and its legacy. Additional 

background on the Manhattan Project can be found at: http://energy.gov/

manhattan. To find out more about how to visit the park and what tours are 

available please visit: www.nps.gov/mapr

INITIAL PROPERTIES TO BE INCLUDED IN MPNHP

The Manhattan Project National Historical Park is composed of the three 

principal locations where work was completed as part of the Manhattan Project: 

Oak Ridge, Tennessee; Hanford, Washington; and Los Alamos, New Mexico. 

Each site performed a unique and critical role in the success of the project and 

today plays an important part in preserving the Manhattan Project story. The 

National Park Service plans to have a presence at all three of these locations.

- Brigadier General Leslie Groves

Los Alamos • New Mexico Oak Ridge • Tennessee

Pajanto Rd

Pajanto Rd

Pajanto Rd

E. Jemez Rd

E. Jemez Rd

E. Jemez Rd

501

501

502 502

502

4 4

4

4

4

4

4

Los Alamos

Bandelier 

National 

Monument

Pajarito Site

Los Alamos Historic District

Gun Site

V-Site

Bandelier 

National 

Monument 

Headquarters NORTH

0 1 MILE

Bear Creek Rd

Bear Creek Rd

Melton Valley Dr

Oak Ridge Oak Ridge Turnpike

Clinch River

Clinch River

New Zion Patrol Rd

New Zion Patrol Rd

Doen Patrol Rd

Bethel Valley Rd

Lagoon Rd

Oak Ridge Turnpike

Oak Ridge Hwy

Oak Ridge Hwy

Hickory Creek Rd

Hardin Valley Rd

B lair R d

75

75

40

40

40

40

To Nashville NW 

approx 150 Miles

To Knoxville 

approx.15 miles

X-10 Graphite Reactor

Clinton Engineer 

Works Boundry

Y-12 Buildings 9731 & 9204-3

 Historic District

Oak Ridge

61

61

61

61

62

62

62

162

170

62

95

95

62

95

95

58

58

58

321

327

Blair Rd

NORTH

0 3 MILES

Hanford • Washington

Hanford Reach 

National Monument

Hanford Reach 

National Monument

US Department of Energy

Hanford Site

Hanford Reach 

National 

Monument

182

82

82

82

82

395

241

243

240

240

240

24 24

24

17

26

Richland

Kennewick

Priest 

Rapids Lake

Pasco

Mabton

Mattawa

Beverly Othello

Grandview

Sunnyside

Prosser

Benton City

West 

Richland

Columbia River

Co ul mb ai River

B Reactor

Bruggemann’s

Warehouse

Allard Pump 

House

White Bluffs Bank

Hanford High School

NORTH

0 5 MILES

“In answer to the question, ‘Was the development of the atomic bomb by the United States 

necessary?’ I reply unequivocally, ‘Yes.’ To the question, ‘Is atomic energy a force for good or 

for evil?’ I can only say, ‘As mankind wills it.’”