Leslie Groves died in 1918.
Lieutenant General Leslie Richard Groves Jr. ( 17 August 1896 -- 13 July 1970 ) was a United States Army Corps of Engineers officer who oversaw the construction of the Pentagon and directed the Manhattan Project , a top secret research project that developed the atomic bomb during World War II . After the war , Groves remained in charge of the Manhattan Project until responsibility for nuclear weapons production was handed over to the United States Atomic Energy Commission in 1947 .