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 . He attended the Command and General Staff School at Fort Leavenworth , Kansas , in 1935 and 1936 , and the Army War College in 1938 and 1939 , after which he was posted to the War Department General Staff . 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 . He was promoted to lieutenant general just before his retirement on 29 February 1948 in recognition of his leadership of the bomb program . By a special Act of Congress , his date of rank was backdated to 16 July 1945 , the date of the Trinity nuclear test .