The Sites The Manhattan Project involved a total of over thirty different research and production facilities, but was mostly carried out in three major secret cities and one public site. The four main sites were at Los Alamos, New Mexico; Hanford, Washington; and Oak Ridge, Tennessee. The sites in Tennessee and Washington were chose due to the cheap hydroelectric power that was available. The Los Alamos site in New Mexico was chosen due to its remote location and was the place where the final assembly of the bombs took place. The facilities at Oak Ridge, Tennessee covered over 60,000 acres in the Tennessee Valley. The site was so secret that not even the governor of Tennessee knew that it was being constructed. The main function of the facilities at Oak Ridge was the production of uranium-235 and at one point the facilities of Oak Ridge were consuming 1/6th of the power produced by the entire country. The Hanford, Washington site covered nearly 1000 square miles of sparsely populated farm land. The Hanford facility was the plutonium production center of the Manhattan Project. These three secret cities were not announced to the public until the Hiroshima explosion. Another notable site was called the Chicago pile-1. This is the location of the first controlled nuclear chain reaction. The reactor was called CP-1. Due to the complications of studying nuclear physics, there were many communication issues caused by research being done my numerous Universities and laboratories across the country. By September 1942 it was clear that a single laboratory was needed for the sole purpose of developing nuclear weapons. Vannevar Bush, the head of the civilian Office of Scientific Research and Development, asked Roosevelt to assign control of the operation over to the military. President Roosevelt assigned the task to the Army Corps of Engineers and selected Col. James Marshall to oversee construction of the new factories to enrich uranium and make plutonium. However, Marshall was not a nuclear physicist and was not sure what was required for the new facilities and consequently progress was delayed. Also the project was repeatedly delayed as the war required a lot of resources and was of a higher priority than the experimental Manhattan Project. Vannevar Bush soon became dissatisfied with Marshall's management of the project and chief of Staff George Marshall then directed General Somervell to replace Col. Marshall. It was then that the project received the name The Manhattan District. The name came from the Corps of Engineers tradition of naming districts after the headquarters' city, which at the time were in New York.