B Reactor. Aerial photographs of the 100-B Area of the Hanford Site, near Richland, Washington, USA, in January 1945. This view includes B Reactor, the first large-scale nuclear reactor ever built. This view looks to the north-west, and is one of the first photographs released to the public of this site. The reactor was built from 1943 to 1944. It was part of the Manhattan Project during World War II, used to produce plutonium for the United States nuclear weapons program. The reactor building is at upper right. The site was designated a US National Historic Landmark in 2008. This photograph is part of the Historic American Engineering Record.