The Pentagon: World’s Largest Low-Rise Office Building

Overview and Location

The Pentagon is the headquarters of the United States Department of Defense, located in Arlington County, Virginia, across the Potomac River from Washington, D.C. Source 1. Spanning nearly 29 acres, the five-sided building contains 17.5 miles of corridors and serves as the central command hub for all three U.S. military services. Source 10

Historical Background

Conceived in summer 1941 to meet urgent wartime office needs, the Pentagon was completed in just 16 months. Source 6 Originally housing the Department of War—now the Department of Defense—it remains a symbol of American military coordination.

Size and Capacity

With three times the floor space of the Empire State Building, the Pentagon is recognized as the world’s largest low-rise office building. Source 2 It accommodates roughly 23,000 military and civilian personnel, making it a self-contained city of defense operations. Source 10

Mission and Operations

The Pentagon supports the DoD mission “to provide the military forces needed to deter war and ensure the nation’s security.” Source 4 All three military departments operate under one roof, streamlining command and communication across the armed forces. Source 7

Visiting the Pentagon

Public tours are available but require advance registration and strict security screening. Source 3 The 200-acre complex includes visitor parking, memorials, and accessible spaces—such as five designated disabled-visitor spots in South Parking. Source 9

FAQ

How many people work at the Pentagon? Approximately 23,000 military and civilian employees.

Can the public tour the Pentagon? Yes—tours are offered, but visitors must register in advance and follow strict security procedures.

Why is the building five-sided? The unique shape was chosen to fit the original site boundaries and maximize office space within a tight construction timeline.

How long did it take to build the Pentagon? Construction began in 1941 and was finished in just 16 months.

Is the Pentagon still the headquarters of the Department of Defense? Yes—it remains the central hub for all three U.S. military services and top-level defense leadership.