Mound Laboratory, named for the nearby pre-historic Miamisburg Mound, was begun in 1946 by the Manhattan Engineer District of the War Department and consolidated production of the nuclear-reaction initiators developed for the United States’ first atomic bombs during World War II. Earlier, from 1943 to 1946, the separation, purification, and processing of polonium for these initiators had taken place at facilities throughout the Dayton area. It became the first permanent post-World War II Atomic Energy Commission site, with 116 buildings and a peak work force of approximately 2,500 scientists, engineers, and skilled workers. Monsanto operated the site from 1947 to 1988, Edgerton, Germeshausen, and Grier from 1988 to 1997, and Babcock and Wilcox from 1997 to 2002. From 1948 to 2003, the U.S. Atomic Energy Commission and the Department of Energy ran it as an integrated research, development, and production center whose missions included the invention of the radioisotope thermoelectric generator, the fueling of nearly 2,500 polonium-210 and plutonium-238 heat sources, and the assembly and testing of RTGs. These devices powered instruments on spacecraft that flew in the orbits of the sun, Earth, Jupiter, and Saturn, traveled to the moon and Mars, and made flybys of Uranus and Neptune. Project work ended in 1994, the RTG program ended in 2003, and shutdown, cleanup, and transfer of reusable buildings to the City of Miamisburg followed, with cleanup and environmental restoration completed in 2010.