The Pentagon The Pentagon is the headquarters of the United States Department of Defense , located in Arlington County , Virginia . As a symbol of the U . S . military , " the Pentagon " is often used metonymically to refer to the U . S . Department of Defense rather than the building itself . Designed by American architect George Bergstrom ( 1876 – 1955 ) , and built by general contractor John McShain of Philadelphia , the building was dedicated on January 15 , 1943 , after ground was broken for construction on September 11 , 1941 . General Brehon Somervell provided the major motive power behind the project ; Colonel Leslie Groves was responsible for overseeing the project for the U . S . Army . The Pentagon is a large office building , with about , of which are used as offices . Approximately 28 , 000 military and civilian employees and about 3 , 000 non - defense support personnel work in the Pentagon . It has five sides , five floors above ground , two basement levels , and five ring corridors per floor with a total of of corridors . The Pentagon includes a five - acre ( 20 , 000 m ) central plaza , which is shaped like a pentagon and informally known as " ground zero , " a nickname originating during the Cold War and based on the presumption that the Soviet Union would target one or more nuclear missiles at this central location in the outbreak of a nuclear war . On September 11 , 2001 , exactly sixty years after the building ' s groundbreaking , a Boeing 757 - 223 , American Airlines Flight 77 , was hijacked by terrorist s and crashed into the western side of the Pentagon , killing 189 people ( the five hijackers , 59 others aboard the plane , and 125 in the building ) . It was the first significant foreign attack on the capital ' s U . S . government facilities since the Burning of Washington by the British during the War of 1812 . History . Construction . Before the Pentagon was built , the United States Department of War was headquartered in the Greggory Building , a temporary structure erected during World War I along Constitution Avenue on the National Mall . The War Department , which was a civilian agency created to administer the U . S . Army , was spread out in additional temporary buildings on National Mall , as well as dozens of other buildings in Washington , D . C . , Maryland and Virginia . 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 . When World War II broke out in Europe , the War Department rapidly expanded in anticipation that the United States would be drawn into the conflict . Secretary of War Henry L . Stimson found the situation unacceptable , with the Munitions Building overcrowded and the department spread out . Stimson told President Franklin D . Roosevelt in May 1941 that the War Department needed additional space . On July 17 , 1941 , a congressional hearing took place , organized by Virginia congressman Clifton Woodrum , regarding proposals for new War Department buildings . Woodrum pressed Brigadier General Eugene Reybold , who was representing the War Department at the hearing , for an " overall solution " to the department ' s " space problem " rather than building yet more temporary buildings . Reybold agreed to report back to the congressman within five days . The War Department called upon its construction chief , General Brehon Somervell , to come up with a plan . Government officials agreed that the War Department building should be constructed across the Potomac River , in Arlington , Virginia . Requirements for the new building were that it be no more than four stories tall , and that it use a minimal amount of steel . The requirements meant that , instead of rising vertically , the building would be sprawling over a large area . Possible sites for the building included the Department of Agriculture ' s Arlington Experimental Farm , adjacent to Arlington National Cemetery , and the obsolete Washington Hoover Airport site . The site originally chosen was Arlington Farms which had a roughly pentagonal shape , so the building was planned accordingly as an irregular pentagon . Concerned that the new building could obstruct the view of Washington , D . C . from Arlington Cemetery , President Roosevelt ended up selecting the Hoover Airport site instead . The building retained its pentagonal layout because a major redesign at that stage would have been costly , and Roosevelt liked the design . Freed of the constraints of the asymmetric Arlington Farms site , it was modified into a regular pentagon . On July 28 Congress authorized funding for a new Department of War building in Arlington , which would house the entire department under one roof , and President Roosevelt officially approved of the Hoover Airport site on September 2 . While the project went through the approval process in late July 1941 , Somervell selected the contractors , including John McShain , Inc . of Philadelphia , which had built Washington National Airport in Arlington , the Jefferson Memorial in Washington , and the National Naval Medical Center in Bethesda , Maryland , along with Wise Contracting Company , Inc . and Doyle and Russell , both from Virginia . In addition to the Hoover Airport site and other government - owned land , construction of the Pentagon required an additional , which were acquired at a cost of $ 2 . 2 million . The Hell ' s Bottom neighborhood , a slum with numerous pawnshops , factories , approximately 150 homes , and other buildings around Columbia Pike , was also cleared to make way for the Pentagon . Later of land were transferred to Arlington National Cemetery and to Fort Myer , leaving for the Pentagon . Contracts totaling $ 31 , 100 , 000 were finalized with McShain and the other contractors on September 11 , and ground was broken for the Pentagon the same day . Among the design requirements , Somervell required the structural design to accommodate floor loads of up to 150 pounds per square foot , which was done in case the building became a records storage facility at some time after the end of the current war . A minimal amount of steel was used as it was in short supply during World War II . Instead , the Pentagon was built as a reinforced concrete structure , using 680 , 000 tons of sand dredged from the Potomac River , and a lagoon was created beneath the Pentagon ' s river entrance . To minimize steel , concrete ramps were built rather than installing elevators . Indiana limestone was used for the building ' s façade . Architectural and structural design work for the Pentagon proceeded simultaneously with construction , with initial drawings provided in early October 1941 , and most of the design work completed by June 1 , 1942 . At times the construction work got ahead of the design , with different materials used than specified in the plans . Pressure to speed up design and construction intensified after the attack on Pearl Harbor on December 7 , 1941 , with Somervell demanding that of space at the Pentagon be available for occupation by April 1 , 1942 . David J . Witmer replaced Bergstrom as chief architect on April 11 after Bergstorm resigned due to charges , unrelated to the Pentagon project , of improper conduct while he was president of the American Institute of Architects . Construction of the Pentagon was done during the period of racial segregation in the United States . This had structural consequences to the design of the building . Under the supervision of colonel Leslie Groves , the decision to have separate eating and lavatory accommodations for whites and blacks was made and carried out . The dining areas for blacks were put in the basement and on each floor there were double toilet facilities separated by gender and race . These measures of segregation were said to have been done in compliance with the state of Virginia ’ s racial laws . The Pentagon as a result has twice the number of toilet facilities needed for a building of its size . President Roosevelt had made an order ending such racial discrimination in the U . S . military in June 1941 . When the President visited the Pentagon before its dedication , he questioned Groves regarding the number of washrooms and ordered him to remove the “ Whites Only ” signs . Until 1965 the Pentagon was the only building in Virginia where segregation laws were not enforced . The soil conditions of the Pentagon site , located on the Potomac River floodplain , presented challenges to engineers , as did the varying elevations across the site , which ranged from above sea level . Two retaining walls were built to compensate for the elevation variations , and cast - in - place ( Franki ) piles were used to deal with the soil conditions . Construction of the Pentagon was completed in approximately 16 months at a total cost of $ 83 million . The building is tall , and each of the five sides of the building is long . Because of the pressing needs of the war , people started working in the Pentagon before it was completed . The Pentagon was built wing at a time , and after the first wing was finished , employees started to move into that wing while construction was continuing on the other wings . Protests . The Pentagon became a spot for protests against the Vietnam War during the late 1960s . A group of 2 , 500 women , organized by Women Strike for Peace , demonstrated outside of Secretary of Defense Robert S . McNamara ' s office at the Pentagon on February 15 , 1967 . In May 1967 , a group of 20 demonstrators held a sit - in outside the Joint Chiefs of Staff ' s office , which lasted four days before they were arrested . In one of the better known incidents , on October 21 , 1967 , some 35 , 000 anti - war protesters organized by the National Mobilization Committee to End the War in Vietnam , gathered for a demonstration at the Defense Department ( the " March on the Pentagon " ) , where they were confronted by some 2 , 500 armed soldiers . During the protest , a famous picture was taken , where George Harris placed carnations into the soldiers ' gun barrels . The march concluded with an attempt to " exorcise " the building . On May 19 , 1972 , the American radicals known as the Weather Underground Organization successfully planted and detonated a bomb in a fourth - floor women ' s restroom in the Pentagon . They announced it was in retaliation for the Nixon administration ' s bombing attacks on Hanoi during the final stages of the Vietnam War . On March 17 , 2007 , 4 , 000 to 15 , 000 people ( estimates vary significantly ) protested against the Iraq War . The protesters marched from the Lincoln Memorial , down Washington Boulevard to the Pentagon ’ s north parking lot . Renovation . From 1998 to 2011 , the Pentagon underwent a major renovation , known as the " Pentagon Renovation Program " . This program , completed in June , 2011 , involved the complete gutting and reconstruction of the entire building in phases to bring the building up to modern standards , removing asbestos , improving security , providing greater efficiency for Pentagon tenants , and sealing of all office windows . As originally built , most Pentagon office space consisted of open bays which spanned an entire ring . These offices used cross - ventilation from operable windows instead of air conditioning for cooling . Gradually , bays were subdivided into private offices with many using window air conditioning units . With renovations now complete , the new space includes a return to open office bays , a new Universal Space Plan of standardized office furniture and partitions developed by Studios Architecture . September 11 attacks . On September 11 , 2001 , the 60th anniversary of The Pentagon ' s groundbreaking , a team of five al - Qaeda affiliated hijackers took control of American Airlines Flight 77 , " en route " from Washington Dulles International Airport to Los Angeles International Airport , and deliberately crashed the Boeing 757 airliner into the western side of the Pentagon at 9 : 37 am EDT as part of the September 11 attacks . All 64 people on the airliner were killed as were 125 people who were in the building . The impact of the plane severely damaged the structure of the building and caused its partial collapse . At the time of the attacks , the Pentagon was under renovation and many offices were unoccupied , resulting in fewer casualties . Only 800 of 4 , 500 people who would have been in the area were there because of the work . Furthermore the area hit , on the side of the Heliport façade , was the section best prepared for such an attack . The renovation there , improvements which resulted from the Oklahoma City bombing , had nearly been completed . It was the only area of the Pentagon with a sprinkler system , and it had been reconstructed with a web of steel columns and bars to withstand bomb blasts . The steel reinforcement , bolted together to form a continuous structure through all of the Pentagon ' s five floors , kept that section of the building from collapsing for 30 minutes — enough time for hundreds of people to crawl out to safety . The area struck by the plane also had blast - resistant windows — 2 inches thick and 2 , 500 pounds each — that stayed intact during the crash and fire . It had fire doors that opened automatically and newly built exits that allowed people to get out . Contractors already involved with the renovation were given the added task of rebuilding the sections damaged in the attacks . This additional project was named the " Phoenix Project " , and was charged with having the outermost offices of the damaged section occupied by September 11 , 2002 . When the damaged section of the Pentagon was repaired , a small indoor memorial and chapel were included , located at the point of impact . For the fifth anniversary of the September 11 , 2001 attacks , a memorial of 184 beams of light shone up from the center courtyard of the Pentagon , one light for each victim of the attack . In addition , an American flag is hung each year on the side of the Pentagon damaged in the attacks , and the side of the building is illuminated at night with blue lights . After the attacks , plans were developed for an outdoor memorial , with construction underway in 2006 . The Pentagon Memorial , which consists of a park with 184 benches on of land , according to the victims ' ages , from 3 to 71 , was opened to the public on September 11 , 2008 . Shooting incidents . On March 4 , 2010 , at 6 : 40 pm , two police officers working for the Pentagon Force Protection Agency were shot at near an entrance to the Pentagon and fired back with their pistols at the suspect . The officers were slightly injured but were treated in a hospital and released . The suspect , identified as John Patrick Bedell ( aged 36 ) , died at the hospital . No clear motive was established . On October 19 , 2010 , shortly before 5 am , an unidentified gunman shot at the south side of the building , shattering windows on the third and fourth floors . Earthquake . On August 23 , 2011 , a 5 . 8 magnitude earthquake in Mineral , Virginia , shook the Pentagon . The building suffered minor damage , with flooding from broken pipes . Layout . The Pentagon building spans , and includes an additional as a central courtyard . Starting with the north side and moving clockwise , its five façades are the Mall Terrace Entrance façade , the River Terrace Entrance façade , the Concourse Entrance ( or Metro Station ) façade , the South Parking Entrance façade , and the Heliport façade . On the north side of the building , the Mall Entrance , which also features a portico , leads out to a long terrace that is used for ceremonies . The River Entrance , which features a portico projecting out , is located on the northeast side , overlooking the lagoon and facing Washington . A stepped terrace on the River Entrance leads down to the lagoon ; and a landing dock was used until the late 1960s to ferry personnel between Bolling Air Force Base and the Pentagon . The main entrance for visitors is located on the southeast side , where the Pentagon Metro station and the bus station are located . There is also a concourse on the southeast side of the second floor of the building , which contains a mini - shopping mall . The Pentagon ' s south parking lot is located on the southwest side of the Pentagon , and the west side of the Pentagon faces Washington Boulevard . The concentric rings are designated from the center out as " A " through " E " ( with in addition " F " and " G " in the basement ) . " E " Ring offices are the only ones with outside views and are generally occupied by senior officials . Office numbers go clockwise around each of the rings , and have two parts : a nearest - corridor number ( 1 to 10 ) followed by a bay number ( 00 to 99 ) , so office numbers range from 100 to 1099 . These corridors radiate out from the central courtyard , with corridor 1 beginning with the Concourse ' s south end . Each numbered radial corridor intersects with the corresponding numbered group of offices ( for example , corridor 5 divides the 500 series office block ) . There are a number of historical displays in the building , particularly in the " A " and " E " rings . Floors in The Pentagon are lettered " B " for Basement and " M " for Mezzanine , both of which are below ground level . The concourse is located on the second floor at the metro entrance . Above ground floors are numbered 1 to 5 . Room numbers are given as the floor , concentric ring , and office number ( which is in turn the nearest corridor number followed by the bay number ) . Thus , office 2B315 is on the second floor , B ring , and nearest to corridor 3 ( between corridors 2 and 3 ) . One way to get to this office would be to go to the second floor , get to the A ( innermost ) ring , go to and take corridor 3 , and then turn left on ring B to get to bay 15 . It is possible for a person to walk between any two points in the Pentagon in less than seven minutes . Just south of the Pentagon are Pentagon City and Crystal City , extensive shopping and high - density residential districts in Arlington . Arlington National Cemetery is to the north . The Washington Metro Pentagon station is also located at the Pentagon , on the Blue and Yellow Lines . The Pentagon is surrounded by the relatively complex Pentagon road network . The United States Postal Service has established six ZIP Code s for The Pentagon , to which the place name “ Washington , D . C . ” is assigned , even though The Pentagon is actually located in Virginia . The Secretary of Defense , the Joint Chiefs of Staff , and the four service branches each have their own designated ZIP Code . Security . The Pentagon Force Protection Agency ( PFPA ) is a United States government agency composed of sworn federal police officers , the United States Pentagon Police and civilian CBRN technicians , and non - sworn civilian anti - terrorism investigative and physical security personnel , and is responsible for the protection of the Pentagon . The Department of Defense created the PFPA after the September 11 , 2001 attacks . The new agency absorbed the Defense Protective Service ( DPS ) and assumed its role of providing basic law enforcement and security for the Pentagon and Department of Defense sites in the 280 acre ( 1 . 1 km ) " Pentagon Reservation " and greater National Capital Region ( NCR ) . PFPA was also charged with providing force protection against the full spectrum of potential threats through robust prevention , preparedness , detection , and response measures . The United States Pentagon Police is the primary federal law enforcement arm of the Pentagon Force Protection Agency . Services . The Pentagon has over 20 of its own fast food operations , including Subway , McDonald ' s , Dunkin ' Donuts , Panda Express , Starbucks and Sbarro , among others . A multibranded KFC , Pizza Hut , and Taco Bell restaurant opened in 2003 , when renovations to the food court were completed . Food services are managed by the Navy Exchange . The Center Courtyard Cafe reopened in the spring of 2008 , replacing the " Ground Zero Cafe " snack bar that was previously there . The " Pentagon Athletic Center " ( PAC ) , a fitness center for military and civilian staff , opened in 2004 adjacent to the north side of the Pentagon , replacing the Pentagon Officers Athletic Club ( POAC ) which had operated for 55 years in a structure between Route 110 and the parade grounds . Each year , the Pentagon grounds are a major focus for hosting the Marine Corps Marathon and the Army Ten - Miler running events . There is a " Meditation and Prayer Room " in the Pentagon , which was dedicated on December 14 , 1970 , by Secretary of Defense Melvin Laird . In conjunction with the 1976 American Bicentennial , the Pentagon began offering guided tours to the general public . Tours were suspended after the September 11 , 2001 attacks , but are currently available on an arranged basis to the general public . Other uses . The Pentagon and its parking lots are used as a staging area for a number of large events , including the Army Ten - Miler , the Marine Corps Marathon and Rolling Thunder motorcycle ride . In 2005 the Department of Defense organized the " America Supports Your Freedom Walk " in the parking lot , an event held to show solidarity with the department ' s current and former employees . The roads of the Pentagon Reservation are routinely used daily by thousands of commuters between Arlington , Virginia and Washington , DC . References . Notes Bibliography