Manhattan Project National Historical Park

Put on your dancing shoes, another season of Tennis Court Dances is in full swing at the Jackson Square Tennis Courts. Held monthly on the third Thursday, Manhattan Project National Historical Park recreates the open-air tennis court dances held in Oak Ridge during the Manhattan Project to entertain the 75,000 war workers and their families contained within America’s Secret City.

For more information on this free and accessible program, please visit: https://www.nps.gov/planyourvisit/event-details.htm?id=3CE60324-B09B-E05D-8E922DE8E7B9319C

Image Credit: US Department of Energy/Ed Westcott

Wartime Oak Ridge was sustained by a flow of commuters, the majority of whom passed over the Solway and Edgemoor Bridges. Built by Knox and Anderson Counties, these bridges predate World War II and were controlled by the Manhattan Project when the fence was built around Oak Ridge. In 1943, under pressure from Tennessee Governor William Cooper, the Army agreed to pay Knox County $25,000 annually ($450,000 in 2024 dollars) for use of Solway Bridge and maintenance of the Oak Ridge approach roads in Knox County.

By early 1944, heavy traffic into Oak Ridge had damaged the roads reducing the speed limit approaching the bridge to only 10 miles per hour. With heavy spring rains, the road washed out in February 1944. With no way to compel Anderson County to make repairs, Oak Ridge contractors began maintaining over 45 miles of Knox County roads.

Image Caption: The Solway Bridge pictured in 1943.

Image Credit: US Department of Energy/Ed Westcott

At the onset of the Manhattan Project, leadership became concerned with recruiting and retraining young scientists and engineers, especially as draft regulations became increasingly strenuous. On May 22, 1943, the Army established a Special Engineer Detachment (SED). The first SEDs arrived in Oak Ridge by late July, followed shortly with a company in Los Alamos by August 1943. By the end of the war, Los Alamos would employ over 1800 SEDs and Oak Ridge had over 1200.

A SED, Val Fitch, later remembered this from his time in Los Alamos, “We lived in single floor barracks, roughly 60 men to a unit… We ate in an army mess hall… We lined up each week to get fresh linen, and once a month to get paid. Reveille came at 6 am, and we had calisthenics from 6:30 to 7:00. We could not leave the barracks for work on Saturday mornings until after inspection of quarters, nominally at 8:00. We worked in… the Tech Area six days a week. It was the army and still it wasn't the army because in the Tech Area we worked alongside, and were beholden to, civilians.”

Image Credit: US Department of Energy/Ed Westcott

🚴‍♂️ Ride with a Ranger — June 13!
Get your tickets while they last!

Register today for Ride with a Ranger on Saturday, June 13, from 9:00 am to 12:00 pm (PDT) in Richland, WA!
Join us for a 17-mile round trip bike ride along the along the Sacagawea Heritage Trail, on city streets through the Richland Parkway, and then continuing along the river to the REACH Museum.

We'll depart from the tennis courts in Leslie Groves Park and make our way to the REACH, where participants can enjoy:
• Hands on activities
• Programs about the Manhattan Project and local plants and animals
• Museum exhibits
Afterward, ride back to Leslie Groves Park with the rangers or on your own.

⭐ This event is FREE, but registration is required.
Registration is open now and closes on June 11 at 6:00 pm.
Thanks to Bike Tri Cities, museum admission is covered for all registered participants!
👉 Learn more and register: https://www.biketricities.org/event-6664724

Image Credit: NPS/REACH Museum

On this day 82 years ago, 6939 allied vessels comprising the largest amphibious invasion in history approached the coast of Normandy, France. Over 150,000 allied soldiers landed on the beaches that morning in an effort to open a second front against N**i Germany and hasten the end of World War II.

The evening prior, US General Dwight D. Eisenhower, commander of the Allied Expeditionary Force, released the following message to the troops:

"Soldiers, Sailors, and Airmen of the Allied Expeditionary Force!
You are about to embark upon the Great Crusade, toward which we have striven these many months. The eyes of the world are upon you. The hope and prayers of liberty-loving people everywhere march with you. In company with our brave Allies and brothers-in-arms on other Fronts, you will bring about the destruction of the German war machine, the elimination of N**i tyranny over the oppressed peoples of Europe, and security for ourselves in a free world.

Your task will not be an easy one. Your enemy is well trained, well equipped and battle-hardened. He will fight savagely.

But this is the year 1944! Much has happened since the N**i triumphs of 1940-41. The United Nations have inflicted upon the Germans great defeats, in open battle, man-to-man. Our air offensive has seriously reduced their strength in the air and their capacity to wage war on the ground. Our Home Fronts have given us an overwhelming superiority in weapons and munitions of war, and placed at our disposal great reserves of trained fighting men. The tide has turned! The free men of the world are marching together to Victory! I have full confidence in your courage, devotion to duty and skill in battle. We will accept nothing less than full Victory!

Good luck! And let us beseech the blessing of Almighty God upon this great and noble undertaking."

Image Caption: General Dwight D. Eisenhower speaking to paratroopers shortly before D-Day.
Image Credit: US National Archives & Records Administration

Beginning construction in Oak Ridge in June 1943, the K-25 Gaseous Diffusion Plant, with its distinctive U shape, was the largest building in the world during the Manhattan Project. Covering a 44-acre tract over one-half mile long and 1,000 feet wide, this top-secret facility employed over 10,000 workers at its height of operation in 1945.

The K-25 Gaseous Diffusion Plant, along with two other nearby massive Manhattan Project facilities, the Y-12 Electromagnetic Isotope Separation Plant and the S-50 Liquid Thermal Diffusion Plant, operated with the intent of enriching or separating lighter uranium-235 from heavier uranium-238.

Unlike the processes used at Y-12 and S-50, K-25 relied on over 3,000 gaseous diffusion steps through which uranium hexafluoride gas could pass through. This process allowed for smaller uranium-235 atoms to pass through the tiny pores in the barriers of each step, enriching the gas and creating a higher concentration of uranium-235. This gaseous diffusion method proved cheaper and more efficient than Y-12's electromagnetic separation process and S-50's liquid thermal diffusion process. Uranium-235 enriched at S-50, K-25, and Y-12 was used in Little Boy, the atomic bomb dropped on Hiroshima, Japan on August 6th, 1945.

The K-25 complex produced enriched uranium for defense and commercial purposes until the mid 1980s. Its benchmark gaseous diffusion method was the only uranium enrichment method used by the United States during the Cold War. In 2013, due to its deteriorated condition, Department of Energy contractors demolished K-25.

Image Credit: US Department of Energy/Ed Westcott

Lottery Opens Today, June 1, for Behind the Fence Tours at Los Alamos

Los Alamos National Laboratory, in collaboration with the National Nuclear Security Administration’s Los Alamos Field Office and the National Park Service, is opening the lottery from June 1 to June 12 for its second 2026 series of public “behind-the-fence” tours of Manhattan Project National Historical Park. Tours will take place twice each day on October 13, 14 and 15.

For lottery information: https://www.lanl.gov/media/news/0518-mapr-tours

Image Credit: Los Alamos National Laboratory

Learn to fish in Oak Ridge!

Youth, ages 12 and younger, are invited to join the Oak Ridge, Tennessee unit of Manhattan Project National Historical Park for a summer of fishing education beginning June 20 from 11am-12pm.

This free program requires registration and space is limited. Registration for the June 20th program lasts from June 1 – June 12. More information on the program and registration can be found at: go.nps.gov/FishInOakRidge

This program was made possible with a grant from the National Park Foundation.

Image Credit: NPS

For the 509th Composite Group, the unit given the responsibility of delivering the atomic bombs, security was a major concern right from the beginning. When Paul Tibbets was assigned to lead, he was given the choice of three air bases for the exclusive use of his project, and chose the one in Wendover, Utah. That December when the 509th was formally created, he made it very clear to the men that there would be no excuse for lapses in security, and throughout their existence made it clear that he meant it. The 509th included not only the plane crews, but the 309th Air Service Group, 603rd Air Engineering and 1027th Materiel Squadrons, 320th Troop Carrier Squadron, 1395th Military Company, and the 1st Ordnance Squadron. When they were in place on Tinian Island in the Pacific Theater, the group of scientists from Los Alamos, designated the 1st Technical Detachment, arrived to do final assembly of the bombs. This combination made them entirely self-sufficient, so there was little need for them to interact with other groups. On Tinian they were located in an isolated area, off-limits to others.

One of the essential aspects of this self-sufficiency was the ability of their maintenance crews to take care of anything the planes needed, from minor adjustments to engine replacements. No other maintenance crews needed to work on the planes or know about their classified modifications, which included reversible-pitch propellers, enlarged bomb bays, British single-point bomb releases, fuel injection, a weaponeer station, and minimal armor and armament.

Image Caption: The B-29 Superfortress Enola Gay lands at Tinian shortly after dropping the Little Boy atomic bomb on Hiroshima.

Image Credit: US Air Force