Pentagon (Five-Sided Building)

The Pentagon, as its name suggests, is based on the number 5: it consists of 5 sides, 5 floors, and a central courtyard covering an area of 5 acres.

Construction Period: 1941 – 1943

Location: Arlington, Virginia, USA

When considering the largest office building in the world, which has a total floor area of 616,518 square meters (6.6 million square feet) and is 28.15 kilometers along the Virginia bank of the Potomac River, across from Washington, D.C., where the Department of Defense and the U.S. Army, Navy, and Air Force are headquartered. The floor area is three times that of the Empire State Building, while the U.S. Capitol (the Congress building) is only equivalent to one of the Pentagon’s five sides. Despite its massive size, the Pentagon is designed for efficiency: 10 corridors radiate like spokes connecting different parts of the building, allowing one to walk to any point within 7 minutes.

Designed by George Edwin Bergstrom and constructed between 1941 and 1943, the five-sided building is in the Neoclassical style, reminiscent of historic fortification structures. However, the Pentagon goes beyond previous constructions in its conceptualization of five sides: the structure includes five pentagonal shapes, not counting the mezzanine and various basement levels, with the main courtyard occupying 5 acres (2 hectares). The distinctive cross-section of the Pentagon is influenced not only by fortification design but also by the original planned location being pentagonal. Ultimately, even while the building was under construction at a different site, the five-sided design remained a prominent feature.

The Pentagon with the Potomac River (Photo: inn-dc)

Built to unify 17 U.S. War Departments into one agency, the Pentagon is an engineering marvel, completed in just 16 months. Major General Brehon B. Sommervell, head of the Construction Division of the Army Corps of Engineers, grasped the idea of a monumental project and emphasized the basic layout of the building, initially intended as a temporary facility to be constructed within 4 days. Construction began immediately after the site was cleared due to the expansion.

The Pentagon under construction, completed in just 16 months.

When ready, engineers had to move 4.2 million cubic meters of earth and 41,492 concrete piles for foundation work. The Potomac River also served as a source of construction materials: extracting 617,000 tons of sand and gravel, which was later processed into 332,000 cubic meters of concrete. As World War II approached, there was a shortage of structural steel in the U.S., leading to the practical decision to use reinforced concrete as the primary construction material, along with Indiana limestone for the exterior facade. Coincidentally, the amount of concrete used was sufficient to build a large warship.

With strict oversight of the construction progress, groundbreaking began in August 1941, with multiple shifts of 13,000 workers working day and night, 7 days a week, and over 1,000 architects working in nearby hangars to draft construction plans as the project progressed. Workers could start their shifts as soon as a section of the building was completed, and over 300 staff moved into the first completed section in August 1941, with 22,000 by December of that year. To facilitate transportation to and from the monumental site, a 48-kilometer access road was built. The Pentagon also has its own police and fire department, as well as a separate water supply and drainage system. In 1956, a helicopter pad was added, and today it is a complex with its own taxi and bus terminal, as well as a subway stop.

The Pentagon from above; despite its massive size,
the efficient layout allows walking to
any point within just 7 minutes. (Photo: coe.uga)

Since 1993, the Pentagon has undergone a comprehensive renovation project costing $1.2 billion, scheduled for completion in 2006, marking the first renovation since its construction, which not only upgraded communication and electrical equipment but also added office space.

18,581 square meters (200,000 square feet) were added in a newly constructed mezzanine in the basement. Additionally, for the first time, the building was equipped with elevators, totaling 40, and all 7,748 windows were replaced. The renovation team worked on this project similarly to the contractors who built the Pentagon in the 1940s; however, one corner took 13 years to complete compared to the initial 16 months of construction.

However, on September 11, 2001, the Pentagon became the site of an indescribable tragedy when part of the western facade was destroyed by terrorists who crashed a commercial airplane into the building, killing 189 people.

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