National Museum of Nuclear Science & History
Herbert M. Parker (1910-1984) was a British-American medical physicist. He worked at Chicago, Oak Ridge, and Hanford during the Manhattan Project, and is perhaps best known for inventing the rep (a precursor of the rad) and helping develop the rem to measure radiation dosage.
Jacob Epting worked as a carpenter in Oak Ridge, TN from November 1942 to October 1943. While Epting assumed he was building a hospital, he was never formally told about the project he was working on.