The "Gadget" device fully assembled atop the 100-foot firing tower, shortly before the Trinity test. July 15, 1945.

The U.S. Department of Energy (DOE), in the mid-1990s, developed a list of eight Manhattan Project properties that were designated as "Signature Facilities." These properties, taken together, aid the American public with interpreting the mission of the Manhattan Project and the development of an atomic bomb. The goal of DOE was to move forward in preserving and interpreting these properties by integrating departmental headquarters and field activities and joining in a working partnership with all interested outside entities, organizations, and individuals, as well as Congress, state and local governments, DOE contractors, and various other stakeholders.

These Manhattan properties are first-of-a-kind or one-of-a-kind facilities that used some of the century's most innovative and revolutionary technologies. Hanford's B Reactor, which created the plutonium for the Trinity device, was the world's first production reactor. Scientists and engineers designed the K-25 gaseous diffusion plant at Oak Ridge to use a totally untested and unproven technology. The Y-12 Beta-3 Racetracks, the only surviving World War II-era electromagnetic isotope separations equipment in the world, still stand, complete with operator panels and telephone switchboard, almost exactly as they did during the war. The other Signature Facilities include the Metallurgical Laboratory, the X-10 Graphite Reactor, the T Plant Chemical Separations Building, the V-Site Assembly Building/Gun Site, and the Trinity Site. Two of the facilities — the Metallurgical Laboratory at the University of Chicago and the Trinity Site on the White Sands Missile Range near Alamogordo, New Mexico — are not owned by DOE. The other six are the responsibility of DOE.

Learn about the history of the Manhattan Project on this interactive website featuring images, essays, and other resources.

At the request of DOE, the Advisory Council on Historic Preservation in 2001 convened a panel of distinguished historic preservation experts who visited the Signature Facilities, evaluated their historical significance, and developed recommendations and preservation options for DOE's consideration. In its final report to the Secretary of Energy, the panel unanimously agreed with DOE that the Signature Facilities are of extraordinary historical significance and stated that they "deserve commemoration as national treasures." Not only do these facilities qualify as national landmark status properties, the panel concluded that the facilities are also of World Heritage Site significance. The report urged DOE to support efforts to convey the powerful story of the role the Signature Facilities played in one of the paramount events of the twentieth century.

For over a decade, DOE and National Park Service, in cooperation with other federal agencies, state and local governments, and other stakeholders, pursued the possibility of including DOE's most significant Manhattan Project properties within a Manhattan Project national park. After numerous studies and several draft bills, Congress passed the National Defense Authorization Act of 2015, which included provisions authorizing the park to be located at three sites: Oak Ridge, Tennessee; Hanford, Washington; and Los Alamos, New Mexico. President Obama signed the National Defense Authorization Act into law on December 19, 2014.

On November 10, 2015, Secretary of the Interior Sally Jewell and Secretary of Energy Ernest Moniz signed the Memorandum of Agreement between the two agencies defining the respective roles in creating and managing the park. The agreement included provisions for enhanced public access, management, interpretation, and historic preservation. With the signing, the Manhattan Project National Historical Park officially was established.

Of the eight Signature Facilities, the X-10 Graphite Reactor, K-25 Gaseous Diffusion Process Building, Y-12 Beta-3 Racetracks, B Reactor, and V-Site Assembly Building/Gun Site are part of the new park. Additional properties may be added at a later date.

The eight Signature Facilities of the Manhattan Project are: