John Shacter was born in Austria and immigrated to the United States after Hitler came to power in Germany. After receiving a chemical engineering degree from University of Pennsylvania in 1943, he was hired by Union Carbide to work on the Manhattan Project at Columbia University. He then transferred to the K-25 Plant in Oak Ridge, where he was involved in overhauling the plant and greatly reducing the cost of uranium, advancements that helped make the modern nuclear industry possible.