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 States’ 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 nation’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. “The Mound” 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.