The Hanford Engineer Works in Hanford, Washington, was constructed between 1943 and 1945 to create the plutonium 239 and uranium 235 used in the atomic weapons needed for World War II. President Franklin Roosevelt (1882-1945) authorized the Army to become involved in the atomic bomb project in 1941. In 1942, the Manhattan Engineer District (MED) was established within the Army Corps of Engineers (USACE) to oversee the project that would later be known as the Manhattan Project. General Leslie Richard Groves Jr. (1896-1970) was placed in command and selected E.I. du Pont de Nemours & Company as the prime contractor. Originally the plant was to have been built at Oak Ridge, Tennessee, where DuPont already had a plant. However, due to its proximity to Knoxville and the need for more land to construct the plant and an entire town, it was decided that the plutonium plant should be created in a more isolated and larger area. After representatives from the USACE and DuPont searched Northern California and the Pacific Northwest, Hanford Washington, was agreed upon as the construction site.

In 1943, Colonel Franklin T. Matthias (1908-1993) was made site manager of Hanford. The Hanford Engineer Works was constructed from March 1943 to February 1945. In less than two years, the site included more than 51,000 workers, and 1,200 buildings had been created. Roads, railroads, water, electricity, and sewer systems also had to be built to run the plant and for all the employees to utilize. The Hanford camp was built to house the workers who worked on the initial site, and the Richland Village was constructed for the workers and their families who would operate the plant once it was built. Due to the physical isolation of the plant and the confidential nature of the government's mission there, the plant was responsible for the medical and social affairs of the workers. The work force was mostly laborers brought in from outside the eastern Washington area. Recruiters focused on male workers that were not likely to be drafted, either over age thirty-eight or having a family. Wives and children were allowed to live at the site, and amenities such as churches, stores, recreational facilities, gymnasium, bowling alley, library, and softball diamond were constructed. Most living quarters were segregated by sex and race, as were mess halls and taverns.

In 1945, the plutonium created at the Hanford Engineer Works was used in the Trinity Test in New Mexico, as well as the atomic bomb dropped in Nagasaki, Japan. The Hanford site continued to produce plutonium throughout the Cold War era and eventually stopped production in 1988. Environmental cleanup began to reduce contamination after forty years of plutonium production and was estimated to take more than thirty years.