Claim: Leslie Groves oversaw construction.

Lieutenant General Leslie Richard Groves Jr. -LRB- 17 August 1896 -- 13 July 1970 -RRB- 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 .   As the son of a United States Army chaplain , Groves lived at a number of Army posts during his childhood . He graduated fourth in his class at the United States Military Academy at West Point in 1918 and was commissioned into the U.S. Army Corps of Engineers . In 1929 , he went to Nicaragua as part of an expedition whose purpose was to conduct a survey for the Inter-Oceanic Nicaragua Canal . Following the 1931 Nicaragua earthquake , Groves took over responsibility for Managua 's water supply system , for which he was awarded the Nicaraguan Presidential Medal of Merit . 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 .   In 1940 Groves , who `` had a reputation as a doer , a driver , and a stickler for duty '' , became special assistant for construction to the Quartermaster General , tasked with inspecting construction sites and checking on their progress . In August 1941 , he was given responsibility for the gigantic office complex to house the War Department 's 40,000 staff which would ultimately become the Pentagon . In September 1942 , Groves took charge of the Manhattan Project . He was involved in most aspects of the atomic bomb 's development . He participated in the selection of sites for research and production at Oak Ridge , Tennessee ; Los Alamos , New Mexico ; and Hanford , Washington . He directed the enormous construction effort , made critical decisions on the various methods of isotope separation , acquired raw materials , directed the collection of military intelligence on the German nuclear energy project and helped select the cities in Japan that were chosen as targets . Groves wrapped the Manhattan Project in security but failed to prevent the Union of Soviet Socialist Republics from conducting a successful espionage program that stole some of its most important secrets .   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 then headed the Armed Forces Special Weapons Project , which had been created to control the military aspects of nuclear weapons . He was given a dressing down by the Chief of Staff of the United States Army , General of the Army Dwight D. Eisenhower , and told that he would never be appointed Chief of Engineers . Three days later , Groves announced his intention to leave the Army . 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 . He went on to become a vice-president at Sperry Rand .