Overview

The Pentagon is the central headquarters for the United States Department of Defense. Situated in Arlington, Virginia, just across the Potomac River from central Washington, D.C., it houses the offices of military and civilian leaders responsible for national defense policy, planning, and operations. The building is widely recognized for its distinctive five-sided plan and very large floor area, making it one of the world’s largest office buildings.

Design and structure

Its five-sided geometry gives the complex a clear identity: concentric corridors and radial corridors organize workspaces around a series of rings and an open central plaza. The exterior is faced with light-colored limestone, a feature often noted in descriptions of the building and linked to its durability and appearance. The structure includes multiple above-ground floors and lower levels; in total there are several levels used for offices, services and utilities. Despite the building’s size, its layout was planned so that most points can be reached in a few minutes.

History and construction

Construction began in the early 1940s to meet an urgent need for a compact, centralized headquarters during World War II. The design and rapid construction reflected wartime priorities; the building was completed in the early 1940s. Over subsequent decades it has been remodeled and upgraded to support evolving technologies and security needs. The site and the building’s role have been the subject of study and public interest throughout American history.

Function, importance and uses

The Pentagon functions as the administrative and operational hub for the U.S. military. It contains offices for civilian leaders, uniformed service branches, joint organizations and support services. Beyond daily administrative work, the complex hosts strategic planning, logistics, training coordination, and ceremonial activities. It is both an office building and a symbol of the U.S. national defense establishment.

September 11, 2001 and resilience

On September 11, 2001, the building was the target of a terrorist attack when an airliner was deliberately flown into the western side. The impact and subsequent fire caused loss of life and substantial damage to part of the structure. The attack resulted in hundreds of casualties across both the building and the aircraft, and prompted an extensive repair and reinforcement effort that restored and modernized the damaged sections while improving safety measures.

Notable facts and distinctions

  • The Pentagon’s five-sided plan differentiates it from most large office complexes; the shape is a defining feature and often referenced in general descriptions — see pentagonal design.
  • The exterior stone finish is commonly described as limestone; material and appearance are sometimes noted in architectural overviews — see building materials.
  • Although large in total floor area, its interior organization emphasizes short travel times between offices — for further detail consult official references at official building information.
  • The Pentagon’s location and relationship to the nation’s capital are often discussed in geographic and transportation contexts — see regional references at Arlington / Washington area resources.

Together, these aspects make the Pentagon both a practical workplace for tens of thousands of people and a prominent national landmark with historical, architectural, and institutional significance.