Side A: Site of Mound Laboratory (1946-2003). The facilities once here propelled the United States through the Nuclear and Space Ages and were named for the nearby pre-historic Miamisburg Mound. The Manhattan Engineer District of the War Department began construction of Mound Laboratory in 1946. The facility consolidated production of the nuclear-reaction initiators, developed for the United Statesâ€™ first atomic bombs during World War II. Previously (1943-1946), the work to separate, purify, and process the element polonium used in these initiators occurred at facilities throughout the Dayton area. Mound Laboratory was the nationâ€™s first permanent post-WWII Atomic Energy Commission site. Mound Laboratory had 116 buildings and at its peak employed approximately 2,500 scientists, engineers, and skilled workers. Contractors operating at the site were Monsanto (1947-1988), Edgerton, Germeshausen, and Grier (1988-1997), and Babcock and Wilcox (1997-2002). (Continued on other side) Side B: Same. (Continued from other side). The U.S. Atomic Energy Commission and the Department of Energy operated Mound Laboratory as an integrated research, development and production center from 1948-2003. These facilities supported nuclear weapons, energy, and space programs. Assistance for space missions included the invention of the radioisotope thermoelectric generator (RTG), fueled nearly 2,500 polonium-210 and plutonium-238 heat sources, as well as the assembly and testing of RTGs. The devices powered instruments on spacecraft that flew in the orbits of the sun, Earth, Jupiter, and Saturn; those sent to the moon and Mars; and in flybys of Uranus and Neptune. Project work and the RTG program ended in 1994 and 2003, respectively. â€œThe Moundâ€ then began shutdown of operations, site cleanup, and transfer of reusable buildings to the City of Miamisburg. Cleanup and environmental restoration work were completed in 2010.