Main Navy and Munitions Buildings The Main Navy and Munitions Buildings were constructed in 1918 along Constitution Avenue ( then known as B Street ) on Washington , D . C . ' s National Mall ( Potomac Park ) , to provide temporary quarters for the United States Military . Both buildings were constructed by the Navy ' s Bureau of Yards and Docks , with the United States Department of War occupying the Munitions Building . To make the buildings more resistant to fire , the buildings were constructed using concrete . With solid construction , the temporary buildings remained in use long after the end of World War I . In August 1939 , the Secretary of War relocated his offices from the overcrowded State - War - Navy Building ( Old Executive Office Building ) to the Munitions Building . The Department of War headquarters remained in the Munitions Building , through the early years of World War II , until 1942 , when some space became available in the Pentagon , which was under construction . The Munitions Building was turned over to the Navy in 1943 , when the Department of War completely vacated the Munitions Building once construction of the Pentagon was completed . Both buildings suffered serious structural problems in the 1960s . In December 1969 , President Richard Nixon announced that both buildings would be demolished , a plan which was carried out in 1970 . The land was then reclaimed and turned into Constitution Gardens , with the Vietnam Veterans Memorial built near the former Munitions Building site in the early 1980s . Construction . Constructing the Munitions and Main Navy Buildings was an idea conceived by Franklin D . Roosevelt , then the Assistant Secretary of the Navy , who put forth the idea to President Woodrow Wilson . Roosevelt originally suggested a temporary building be placed on the Ellipse , but President Wilson disliked the idea of a building on the White House ' s front lawn . Thus , Roosevelt suggested placing the buildings on the National Mall ( Potomac Park ) along B Street ( renamed Constitution Avenue in 1931 ) , near the Lincoln Memorial . Roosevelt wanted them to be ugly wooden buildings , so that people would want to tear them down right away after World War I . However , to make the buildings more fire resistant , concrete and steel materials were recommended . Roosevelt later expressed regret for allowing these building to be constructed , saying in 1941 , " I didn ' t think I would ever be let into the Gates of Heaven , because I had been responsible for desecrating the parks of Washington . " The project was originally intended for just the Navy , but the Department of War also wanted in on the project , thus two buildings were proposed . With concrete construction not unreasonably more expensive than a wood frame building , Congress accepted the proposal for concrete buildings , and approved the funds for the project in March 1918 . The task of design and construction of the buildings was given to the Navy ' s Bureau of Yards and Docks , and the buildings were completed in 5 months . Munitions Building . The Munitions Building , constructed in 1918 , contained of space across three stories , and was designed to provide temporary accommodations for 9 , 000 Department of War employees . During World War I , the War Department had greatly expanded , and by the end of the war , the Main Navy and Munitions Building together housed 14 , 000 military personnel , including the Secretary of the Navy . A large parking lot wide and long , was located at the rear of the Munitions Building , with space to accommodate approximately 1 , 000 cars . Various small exhibits were on display in the corridors of the Munitions Buildings , showing military uniforms , types of gas masks , military daily rations , and Army photographs . The Munitions Building was separated from the Main Navy Building by a vehicle entryway at 19th Street , and the main entrance of the Munitions Building was located at 20th Street . The Munitions Building had a total of eight wings . At the end of World War I , the Munitions Building housed technical branches , including the Quartermaster General , United States Army Corps of Engineers , Ordnance Corps , Chemical Warfare Service , Signal Corps , and Army Air Service . In March 1923 , the Army ' s Finance Office also moved into the Munitions Building . In February 1924 , plans were put forth to build an oil steam plant for the Main Navy and Munitions Building . In November 1933 , the Army Inspector General ' s office , along with the Organized Reserves , the welfare section of the Secretary ' s office , and the Office of Chief of Chaplains moved into the Munitions Building . The National Guard Bureau also was housed in the Munitions Building , as was the Army Industrial College . Headquarters . At the time when the Munitions Building was constructed , the War Department was headquartered in the State - War - Navy Building , which was completed in 1888 and located on 17th Street NW , next to the White House . By the 1930s , the War Department was being squeezed out by the Department of State , and the White House was also in need of additional office space . In August 1939 , Secretary of War Harry H . Woodring , along with Acting Chief of Staff of the Army George C . Marshall , moved his office into the Munitions Building . In the late 1930s , a new War Department Building was constructed at 21st and C Streets in Foggy Bottom , but upon completion , the new building did not solve the department ' s space problem , and ended up being used by the Department of State . To help deal with the space shortage , a fourth story was added to the Main Navy and Munitions Buildings during World War II . Coming into office , with World War II breaking out in Europe , Secretary of War Henry L . Stimson was faced with the situation of the War Department spread out in numerous buildings across Washington , D . C . , as well as Maryland and Virginia , and the Munitions Building was overcrowded . On July 28 , 1941 , Congress authorized funding for a new Department of War building in Arlington , Virginia , which would house the entire department under one roof . When office space became available in 1942 at the Pentagon in the first completed wing , the Secretary of War vacated the Munitions Building and moved to the Pentagon . The Department of War vacated the Munitions Building in 1943 , once construction of the Pentagon was completed . The Department of Navy took over the Munitions Building once the Department of War relocated out of the building , and placed the Navy ' s Material Systems Command offices in the Munitions Building . World War II . The Signal Intelligence Service was located in the Munitions Building during the early years of World War II . In September 1939 , the Signal Intelligence Service was able to break Japan ' s cipher , Purple . The Department of War continued to receive intercepted messages , codenamed Magic , including final messages to the Japanese Embassy in Washington before the Attack on Pearl Harbor . Main Navy . The Main Navy building was used by the Navy from the time it was built , until it was demolished in 1970 . The building contained of space , nine wings , and was connected to the Munitions Building by an elevated covered walkway . Navy offices housed in the Main Navy building soon after it opened included the Bureau of Navigation , Bureau of Supplies and Accounts , Bureau of Steam Engineering , Bureau of Construction and Repair , the Bureau of Yards and Docks , Bureau of Ordnance , Bureau of Medicine and Surgery , the Secretary of Navy ' s offices , along with Naval Operations , and the Compensation Board . Later on , other Navy Offices moved into Main Navy , including the Dispensary , the Navy Red Cross , Examining Board , and Retiring Board , which were previously housed in Corcoran Courts , an apartment building converted into offices . The Hydrographic Office and United States Marine Corps moved to Main Navy from a Navy Annex building , located at New York Avenue and 18th Street , and the United States Coast Guard relocated from the Munsey Building . The Navy Department Library was relocated to the Main Navy building in 1923 . From 1926 to 1941 , a small reinforced concrete roof penthouse on the Main Navy building was used for radio and communication intercepts training . Criticism . The Main Navy and Munitions Buildings were disliked by many , as going against the intentions of Pierre ( Peter ) Charles L ' Enfant of making the National Mall into an open space surrounded by aesthetically pleasing government buildings . The Munitions and Navy buildings were described as " unsightly shacks , of which many scores sprung up like mushrooms during the war . " Despite their dislike , due to their solid construction , many were concerned that the buildings would remain for a long period . Demolition . By 1960 , the Munitions Building housed approximately 7 , 000 employees of not only the Navy , but also the Army , Air Force , Veterans Administration , and the Department of State . After decades of use , the building experienced structural problems in the late 1950s and 1960s , including cracked concrete piers , numerous interior cracked and bent walls , and settling floors . The buildings , constructed on marshy parkland , were damp and the foundations settling . Portions of the buildings were declared unsafe in 1969 , resulting in approximately 3 , 000 employees relocating to other facilities . In December 1969 , President Richard Nixon announced a plan for demolishing the Main Navy and Munitions Buildings . The plan involved moving Navy employees to new buildings in the Crystal City and Ballston areas in Arlington , Virginia . The Main Navy and Munitions Buildings remained on the Mall until 1970 , when they were demolished . In the 1970s , Constitution Gardens was built on the former site of the Main Navy and Munitions Buildings , and the Vietnam Veterans Memorial was built nearby in the early 1980s .