1949: Mound Laboratory opens. Its top-secret defense research and production included polonium and plutonium processing and the production of nuclear detonators.
1950-1963: Mound scientists experiment with uranium, protactinium-231 and plutonium-239 as part of civilian reactor research.
1954: Mound scientists invent the polonium-fueled radioisotopic thermoelectric generator, which is later used in the space program.
1960-1970: Mound released radioactive tritium into the air.
1969: A pipe break contaminated the soil with plutonium-238. The contamination spread off-site into the Miami-Erie Canal.
1970s: Control over contaminants tightens as the environmental movement takes hold.
1989: The Mound plant is placed on the U.S. Environmental Protection Agency's National Priorities List because of past disposal practices and environmental releases.
1991: The Department of Energy announces plans to close the Mound plant.
1993: Despite efforts by local officials to save Mound, the Clinton administration affirmed the closure decision made under the first President Bush.
1994: Most Mound operations cease. The city creates the Miamisburg Mound Community Improvement Corp. to spearhead redevelopment.
1995: Environmental cleanup of the old Miami-Erie Canal on the site begins. MMCIC leases the first buildings to Mound spinoff businesses.
1997: DOE awards a $501.6 million contract for environmental cleanup with a target completion date of 2001.
1999: MMCIC makes the first roadway and utility improvements.
2002: With the cleanup behind schedule and over budget, DOE awards a $434.7 million contract with a completion date of 2006.
2003: MMCIC builds and leases one 24,000-square-foot building, the nation's first new construction on a former Superfund site.
2005: DOE and EPA deem the cleanup complete, but local officials are dissatisfied with waste remaining at a Mound landfill. U.S. Reps David Hobson and Mike Turner successfully advocated for federal funds to keep the cleanup going.
2006: DOE awards a $73.3 million contract to clean up the old landfill, with a completion target of 2010.
2010: Local officials declare the site cleaned up and ready for full-scale redevelopment.
Sources: Ohio EPA, Miamisburg Mound Community Improvement Corp., Alliance for Nuclear Accountability, Mound Museum Association