
The success of the Manhattan Project put a swift end to a raging world war that had already killed 1.2 million Americans at the time. The project produced Little Boy and Fat Man, the first and only atomic bombs ever dropped. They destroyed the Japanese cities of Hiroshima and Nagasaki, respectively, killing more than 200,000 people, most of them Japanese civilians. It is hoped that something like it will never have to be resorted to again.
But its legacy lies in the way the project was run. It has become a model for large-scale, highly technical, hazardous wartime projects that have to be carried out in utmost secrecy. It was led by the U.S. with support from the UK (which initiated the original Tube Alloys project) and Canada. At the height of its research and development activities, from 1942 to 1946, it was under the direction of Major General Leslie Groves of the U.S. Army Corps of Engineers.
Because we were RVing across North America for eight years, we had the opportunity to learn about the secrets of the Manhattan Project in a way that we never could have just reading about them. In the span of three years, we saw three of the most important sites that contributed to its successful outcome: Oak Ridge, Tennessee; Hanford Reach, Washington; and Los Alamos, New Mexico. In fact, these three sites now jointly comprise the Manhattan Project National Historical Park, which was created in 2015.
Oak Ridge, Tennessee
My husband’s high school classmate was a senior executive at Jacob’s Engineering before his retirement. It is a company that continued to hold major parts of the decommissioning projects of the huge central production facilities of the Manhattan Project in Oak Ridge, Tennessee. In fact, the last part of the decommissioning was scheduled for July 2020. He invited us to his home in Knoxville, Tennessee, only 30 minutes away from the Oak Ridge production facility.
The Production Facility
He took the time to show us the full extent of the facilities at an overlook up a hill near the town. The total footprint at the time it was operational was 43-hectares, with five million square feet of working space on four floors. It was in this small Tennessee town that the biggest buildings in the world were built, and where the biggest (and most significant) industrial projects in the world were run.
What Was Produced Here
The Manhattan Project developed two types of atomic bombs during WWII: a relatively simple gun-type fission weapon using enriched uranium, and a more complex implosion-type atomic bomb using plutonium. Three methods were employed for uranium enrichment. Most of this work was performed at the site in Oak Ridge, which was codenamed “Site X.”
Public Proclamation Number Two declared the facilities in the town a total exclusion area that no one could enter without military permission. It was generally known to be part of “frantic efforts” to make “tuballoy tetroxide,” the code name for 10 to 12 percent enriched Uranium-235. The Oak Ridge population expanded well beyond the initial plans and peaked at 75,000 in May 1945.
The Secret City
We also toured the historic part of town and the visitor center. We learned about how the whole town buzzed with activity during the time. At the end of the day, my husband’s classmate showed us the documentary film The Secret City, which pulled together the whole story. It describes very clearly how the secret was kept. Everyone was sworn to secrecy. And everyone followed. It was the best introduction we could have had, and it inspired us to get an even more comprehensive understanding of the Manhattan Project, which wound up taking us to Hanford Reach, Washington.

Hanford Reach, Washington
Just two months later, we were in Washington, waiting for my Seattle appointment in connection with my application for citizenship. As usual, we looked for national parks or national monuments to visit. While there, we made it to the Hanford Reach National Monument, created in 2000 and named after Hanford Reach, the last non-tidal free-flowing section of the Columbia River.
The National Monument
At the northern end of the Reach are the White Bluffs, white cliffs rising out of the Reach some 400 feet. The lands are home to a wide variety of plants and animals, and the Hanford Reach provides one of the Northwest’s best salmon spawning grounds. Additionally, 48 rare, threatened, and endangered animal species have found refuge on the monument, as have several insect species found nowhere else in the world.
The national monument had been untouched by development or agriculture since 1943 because of the Manhattan Project activities conducted there. In fact, it has been considered an involuntary park, a term coined by science fiction author Bruce Sterling to describe areas that, because of environmental, economic, or political reasons, have been allowed to return to an overgrown, feral state. Other famous examples are Chernobyl and the Korean Demilitarized Zone.
What Was Produced Here
This national monument had been created mostly from the former security buffer surrounding the Manhattan Project National Historic Site. This site consists of seven reactors built to produce plutonium for the more complex Manhattan Project implosion bomb. The site was chosen because Oak Ridge was deemed too close to an urban population center (Knoxville) to risk a tragic nuclear accident. Hanford Reach was farther from Richland, Washington, which wasn’t as big a city as Knoxville. It was also deemed important that the location be as far as possible from Oak Ridge.
The Production Facility
This site was isolated but near the Columbia River, which was an ideal source of cooling water for the reactors. Codenamed “Site W,” by July 1944, some 1,200 buildings had been erected and nearly 51,000 people were living in the construction camp. As a matter of fact, at its peak, the camp was the third most populous town in the state of Washington. It operated a fleet of over 900 buses — more than the city of Chicago. Today, the Hanford Reach Unit of Manhattan Project National Historical Park contains the B Reactor National Historic Landmark, the reactor that produced the plutonium for Fat Man. Reactor C stands close beside it. Interestingly, there is no Reactor A.

Los Alamos, New Mexico
In 2012, we were exploring New Mexico. When we were at Bandelier National Monument, we found out that the Manhattan Project in Los Alamos was just 20 minutes away. So we took a little detour and went to see what has now become the third unit of Manhattan Project National Historical Park.
The Design And Production Facility
Los Alamos was the central design and production facility, codenamed “Site Y.” Again, it was decided that this integral facility should be in a remote but central location separate from Oak Ridge. Robert Oppenheimer, the nuclear physicist who designed the nuclear bombs, recommended that it should be somewhere near Albuquerque where he had a ranch. He was impressed with the views of the Sangre de Cristo Mountains, which would be inspiring for the scientists who would work on the project.
The team of scientists who worked here, which included Enrico Fermi and was led by Oppenheimer, built both atom bombs. We delighted in seeing the cottages on Bathtub Row where they lived. These were the only homes in the facility with bathtubs. General Leslie R. Groves took charge of building and maintaining the infrastructure while the scientists pondered the imponderables. The Bradbury Science Museum tells the whole story and houses what remains of the two bombs.
The Two Bombs
On July 16, 1945, the first-ever atomic bomb was tested and detonated at Trinity Site, southwest of Albuquerque, at New Mexico’s Alamogordo Bombing and Gunnery Range. Today, visits to the site are sponsored by the Alamogordo Chamber of Commerce on the first Saturdays of April and October. The rest of the year, it is closed because it lies within a missile impact zone.
The rest is history. Little Boy, the simpler uranium weapon, was dropped on Hiroshima on August 6, 1945, and three days later, Fat Man, the more complex plutonium bomb, was dropped on Nagasaki. That ended WWII. It cost many lives — and it prevented the loss of millions more had the hostilities lasted for additional months or years.
The Postwar Years
In the immediate postwar years, the Manhattan Project conducted weapons testing, developed new weapons, supported medical research into radiology, and laid the foundations for the nuclear navy. It maintained control over American atomic weapons research and production until the formation of the United States Atomic Energy Commission in January 1947. Finally, its pivotal role promoted the development of the current network of National Laboratories.
These laboratories now number 17 and are at the forefront of scientific research and development, some of which is conducted nowhere else in the world. The Los Alamos National Laboratory that designed and finally assembled the bombs still operates today as part of the network. We want to visit more. It is so interesting and inspiring to see why and how the U.S. was and continues to be at the forefront of science to meet the historic challenges of the world.
Inspired? Read up on five reasons to visit Bletchley Park, home of the codebreakers.